A “casting couch” is a couch that a director or a producer uses to seduce actors or actresses who want acting parts in their productions. The term apparently started on Broadway in New York City. “...to casting-couch producer—the ladder is long, but the dizzying denizens of the Gland Canyon known as Broadway somehow climb it” was cited the book Hangover: A Novel of Broadway Manners (1929) by Max Lief (a former writer on the New York Daily News).
   
It’s not known if American theatrical producer David Belasco (1853-1931) began the “casting couch.” (Belasco’s “original casting couch” is now located at Ten Chimneys,  the home of Broadway actors Lynn Fontanne and Alfred Lunt at Genesee Depot in Wisconsin.) The Shubert Organization has been said to have had a casting couch, especially with chorus girl jobs.
 
The “casting couch” term soon migrated to Hollywood and the film industry. “The casting couch song: ‘You oughta be in pictures’” was printed in the April 1934 “Hollywood” newspaper column of Sidney Skolsky (1902-1983)—the man who coined “Oscar” for “Academy Award” in March 1934.
 
A “casting-couch cougar” was, as a biography of American actress Joan Crawford described it, a sexually active male producer or director. “Cougar” is slang for a sexually active woman who dates significantly younger men, and “casting-couch cougar” in the 2000s reflects this slang use.
   
[This entry includes research from Peter Jenson (who located a relevant 1920 Photoplay citation), George Thompson (who located a stag film titled The Casting Couch) and Ben Zimmer (who found the eBay book flap of Max Lief’s Hangover)  of the American Dialect Society listserv.]
     
   
Wikipedia: Casting couch
The casting couch, casting-couch syndrome, or casting-couch mentality is the trading of sexual favors by an aspirant, apprentice employee, or subordinate to a superior in return for entry into an occupation, or for other career advancement within an organization. The term casting couch originated in the motion picture industry, with specific reference to couches in offices that could be used for sexual activity between casting directors or film producers and aspiring actors. It is not to be confused with the adult entertainment industry where such actions may be a prerequisite, although many pornographic films and pornographic websites play on the casting couch theme and allude to similarities one may find in casting couch scenarios in the film industry.
 
The term is now often used to refer to other industries besides entertainment, though careers which are highly desirable and traditionally difficult to break into, such as the movie, television and music industries, have been the subject of casting couch stories in popular culture. Such trading of favors can be an abuse of power—possibly even statutory rape—and can become a wider sex scandal if deemed newsworthy.
 
(Oxford English Dictionary)
casting-couch  n. colloq. (orig. U.S.) see quots.
1948   H. L. Mencken Amer. Lang. Suppl. II. xi. ii. 704   Terms emanating from Hollywood wits..casting-couch for the divan in a casting-director’s office.
1963   Sunday Express 27 Jan. 22/6   In the old days..the only way anyone got anywhere in this business was by way of the casting couch.
1966   C. Fenn Pyramid of Night ix. 183   Get a load of that casting couch. What girl wouldn’t want to be laid on velvet?
       
eBay
Hangover:
A Novel of Broadway Manners
By Max Lief
New York, NY: Horace Liveright
1929
Front flap:
FROM wisecracker to highjacker, from 15-and-5 taxi driver to $5 cover night club pirate, from beminked show girl to casting-couch producer—the ladder is long, but the dizzying denizens of the Gland Canyon known as Broadway somehow climb it.
       
Newspapers.com
13 October 1929, Miami (FL) Daily News, “The Book Nook” by Barend Beek, society sec., pg. 5, col. 5:
From wisecracker to hi-jacker, from 15-and-5 taxi driver to $5 cover night club pirate, from beminked show girl to casting-couch producer—the ladder is long, but the dizzying denizens of the Gland Canyon known as Broadway somehow climb it.
 
Lantern
28 February 1931, Inside Facts of Stage and Screen, pg. 4, col. 3:
Was the casting director asleep on the casting couch?
i
Newspapers.com
9 April 1934, Daily News (New York, NY), “Hollywood” by Sidney Skolsky, pg. 34, col. 3:
The casting couch song: “You oughta be in pictures.”
   
30 May 1935, The Daily Northwestern (Evanston, IL), “Lefty’s One Night Stand Packs ‘Em In,” pg. 3, col. 1:
“Waiting for Lefty” by Clifford Odets.
(...)
Whole plays have been devoted singly to each of the sparks—racial prejudice, marital difficulties arising out of poverty, thwarted love, the price of “parts” in Broadway plays (“the producer’s casting-couch” is one of Odets’ sardonic quips), the political racket in charity hospitals, the bitter folly of wars, the shadow boxing of vested interests and education, etc., etc. And yet “Waiting for Lefty” is compact and all-of-a-piece, and it has all the impact of a well aimed bomb.
 
Newspapers.com
4 July 1936, Courier-Post (Camden, NJ), “On Broadway” by Walter Winchell (“The American Language” by Jim Tully), pg. 4, col. 8:
Some of the motion-picture terms are very interesting. The divan in a manager’s office is a “casting couch.” ...
 
24 November 1937, Variety (New York, NY), pg. 1, col. 4:
Radio Ed Mixes
Bureau, Couch;
Chi Faces Red
Chicago, Nov. 23.
Larry Wolters, radio ed, bloomered in the Chi Tribune through an evident misconception of show business lingo, and as a result put Columbia, WBBM and the gals in a tough spot. WBBM has set up a casting bureau, and Wolters noted it in this manner:
 
‘WBBM has initiated something it calls a casting couch. All feminine performers seeking jobs at the station must pass an auditioning board of four women occupying the couch. They are Kaye Brinker, Caroll Mountjoy, Helen Keppler Brooks and Gertrude Dyer.’
 
What must have confused Wolters is the fact that at about the same time CBS-WBBM ordered couches out of all offices except those occupied by the three top execs.
   
Lantern
1 December 1937, Broadcasting, pg. 44, col. 2 photo caption:
PICK FEMME TALENT—Gone from radio’s often quaint idiom will be the phrase “casting couch” when stations have a committee of women audition all girl singers and actresses, a plan recently started at WBBM.
 
Google Books
If We Only Had Money
By Lee Shippey
Boston, MA: Houghton Mifflin Company
1939
Pg. 164:
Trade was slack in the little cocktail bar and he struck up conversation with the bartender. ‘Tell me one thing,’ said the bartender, when he had learned that Richie worked in the studio. ’ Is it true about casting couches?’
 
‘Casting couches?’
Pg. 165:
‘Yeah. They say every casting director has a couch in his office, and that’s where a lot of the girls who ask for jobs have to take their tests.’
 
11 October 1941, The Billboard, pg. 17, col. 1:
End of Casting Couches!
PHILADELPHIA, Oct. 4.—State Department of Labor and Industry, regulating the licensing and operations of all agents, has sent out a notice to all the agents ordering that all couches and divans be removed from their offices.
 
Looks like the end of the old gag about “casting couches.”
 
22 October 1947, Variety (New York, NY), pg. 6, col. 2:
CASTING COUCH PITCH
ALMOST SNARES PHONEY
Paramount’s eastern talent staff, a couple detectives and a pair of cynical femmes who refused to fall for the “you-oughta-be-in-the-movies, baby” routine formed a posse in the lobby of the Radio City Musical Hall, N. Y., Monday (20) on a hunt for a phoney talent scout who claimed he repped Paramount. He failed to show up or got suspicious and ducked.
     
Google Books
Modern American Plays
By Frederic G. Cassidy
New York, NY: Longmans, Green
1949  
Pg. 208:
Phil.: What’s that— casting couch?
Sten.: What’s that? You from the sticks?
Phil.: I beg your pardon?
Sten. [rolls up her sleeves, makes elaborate deaf and dumb signs]: No from side walkies of New Yorkie . . . savee?
Phil.: Oh, you’re right. Two years of dramatic stock out of town. One in Chicago.
Sten.: Don’t tell him, Baby Face.
   
Google Books
The Saturday Evening Post
Volume 221
1949
Pg. 36:
The casting couch is celebrated in legend, and it must be admitted that most producers’ private offices boast a large, comfortable couch. The office of Jed Harris at Demos Productions, Inc., 1697 Broadway, has a green leather couch.
 
Google Books
Marilyn Monroe
By Maurice Zolotow
New York, NY: Harcourt, Brace
1960
Pg. 89:
A casting couch is traditional in a producer’s office, but here was a producer’s office with no casting couch or even a non- casting couch, not even a narrow uncomfortable couch.
 
OCLC WorldCat records
Casting couch
Author: John B Thompson
Publisher: Manhasset, N.Y. : Kozy Books, 1962.
Edition/Format:   Print book : Fiction : English
       
Google Books
Downwind of Upstage;
The Art of Coarse Acting
By Michael Frederick Green
New York, NY: Hawthorn Books
1966, ©1964
Pg. 86:
Shun the casting couch. Any director who would cast a woman merely because he has hopes of her favors is simply a human rat, devoid of morals.
 
Google Books
On Stage:
A practical guide to the actor’s craft
By Muriel Steinbeck
Sydney, N.S.W.: Murray
1969
Pg. 127:
And, while I would not be silly enough to say that the “casting couch” does not exist, the young actress who avails herself of it, is invariably bitterly disappointed. It is true that many parts are cast that way.
 
OCLC WorldCat records
Casting couch
Author: Don James
Publisher: Sydney : Free Association Press, 1972, ©1962.
Edition/Format:   Print book : Fiction : English
 
OCLC WorldCat records
The casting couch
Author: Carl Driver
Publisher: San Diego, Calif. : Greenleaf Classics, ©1972.
Series: Pleasure reader, PR346.
Edition/Format:   Print book : Fiction : English
 
OCLC WorldCat records
The casting couch and me : the uninhibited memoirs of a young actress
Author: Joan Wood
Publisher: New York : Walker, 1974, ©1975.
Edition/Format:   Print book : Biography : English
 
OCLC WorldCat record
The casting couch
Author: Selwyn Ford
Publisher: London : Grafton, 1990.
Edition/Format:   Print book : English
   
Google Books 
International Directory of Company Histories, Volume 24
Gale Group
London, UK: St. James Press
1998
Pg. 438 (The Shubert Organization):
According to their biographer, “Although they did not invent the casting couch, it is believed that the Shuberts developed its functions.”
   
Google Books
The Boys from Syracuse:
The Shuberts’ Theatrical Empire
By Foster Hirsch
New York, NY: Cooper Square Press
1998
Pg. 100:
“What they did to those girls wasn’t fair,” according to Agnes de Mille. “If you didn’t sleep with them you didn’t get the part. The Shuberts ran a brothel: let them sue me.”
     
New York (NY) Times
ARTS IN AMERICA: Where Stars Came Out to Play; Broadway’s Rural Refuge, With Lunt and Fontanne
By RICK LYMAN SEPT. 29, 1998
(...)
...Ten Chimneys, the legendary and utterly peculiar summer retreat of Alfred Lunt and Lynn Fontanne, the reigning couple of the American theater.
 
For 30 years, they never accepted a play unless it contained substantial parts for both of them, and they almost never worked in summer, so they could spend it at Ten Chimneys, in the rolling farmland of southeast Wisconsin.
(...)
In a small sitting room was a yellow couch from the office of the Broadway producer David Belasco that the Lunts told people had been ‘‘the original casting couch.’‘
 
OCLC WorldCat record
Tales from the casting couch : an unprecedented candid collection of stories, essays, and anecdotes by and about legendary Hollywood stars, starlets, and wanna-bes ...
Author: Michael Viner; Terrie Maxine Frankel
Publisher: Beverly Hills, Calif. : New Millennium Press, 2001.
Edition/Format:   Print book : Biography : English
   
Google Books
Joan Crawford:
The Essential Biography
By Lawrence J. Quirk and William Schoell
Lexington, KY: The University Press of Kentucky
2002
Pg. 7:
... what she didn’t mention was that Emerine had warned her that Young was a “casting-couch cougar.” Bitterly wise to the male and his ways, Lucille “jumped on Ernie’s couch”—Joan’s words—and he got her a $25-a-week job in a Chicago nightspot.
 
1 August 2002, Knight Ridder Tribune News Service, “Reeling: A dishy biography” by Charles Ealy:.
In Chicago, Joan (Crawford—ed.) was a chorus girl and a “casting-couch cougar.” She also had “brief affairs with other chorus girls.”
 
OCLC WorldCat record
This world. Bollywood : the casting couch
Author: Darius Bazargan; Tanya Datta; British Broadcasting Corporation.
Publisher: London, England : British Broadcasting Corporation (BBC), 2005.
Series: VAST: academic video online
Edition/Format:   eVideo : Clipart/images/graphics : English
Database: WorldCat
Summary:
This documentary, produced and directed by Darius Bazargan, features a behind the scenes look at Bollywood and the casting couch scandal that has rocked this industry.
   
22 July 2006, Winnipeg (Manitoba) Free Press, “Fringe,” pg. C3:
Don’t be put off by the campy promo material promising “comic confessions of a casting couch cougar.”
 
Hamilton comedian Colette Kendall’s alter-ego is a menopausal Hollywood B-movie star with lots of cash and a trail of ex-husbands, but she’s absolutely charming.
 
Google Books
Great Producers:
Visionaries of American Theater
By Iris Dorbian
New York, NY: Allworth Press
2008
Pg. ?:
There are also rumors that the “casting couch”procedure might have started with him(though Belasco was married to Cecelia Loverich for over fifty years, siring two daughters with her).
(American theatrical producer David Belasco, 1853-1931.—ed.)
   
Indiana Repertory Theatre
TALES FROM TEN CHIMNEYS
7/20/2017
BY ROBERT NEAL
(...)
Still another room offers David Belasco’s original, and literal, “casting couch” that the Lunt’s bought from his office after he died.
 
The Atlantic
‘Casting Couch’: The Origins of a Pernicious Hollywood Cliché
How a seemingly innocuous phrase became a metonym for the skewed sexual politics of show business
BEN ZIMMER OCTOBER 16, 2017 3:57 PM ET CULTURE
(...)
The phrase casting couch became linked to the Shuberts, at least in retrospect, as the etymologist Peter Tamony discovered. As recorded in the Historical Dictionary of American Slang, Tamony collected a usage example from 1931, describing an event that “happened some time ago, long before the casting couches were thrown out of the Shubert Building.”
 
By then, however, the idea of the casting couch had moved out west to Hollywood. In a 1920 article in Photoplay magazine, a New York journalist reported on “immorality in camera-land,” where “young women are not advanced in their chosen profession unless they submit to the advances of studio managers, directors, or influential male stars.”
 
The phrase casting couch had evidently not yet become part of Hollywood parlance, since it doesn’t appear in the Photoplay article. But in 1924, a silent stag film may have been responsible for introducing the expression to a wide audience. The film was titled The Casting Couch, and it featured the stereotypical scenario of an actress auditioning for a role and giving in to the salacious demands of the casting director. (It’s hard to know for sure if the title of the film actually dates to 1924, since the surviving prints of such “blue” movies have often been heavily edited after the fact.)