Syndicated newspaper columnist Walter Winchell (1897-1972) introduced the term “moom picher/pitcher/picture” for “motion/moving picture.” This was, supposedly, the New York City dialect in the 1920s.
   
“Moom-pitchers” was cited in print in 1923. “Moom pichers” and “moom picture” were cited in print in 1928, but were possibly used earlier. Winchell’s columns were not yet syndicated in the mid-1920s, and many columns—especially those he wrote for the New York (NY) Evening Graphic—have been lost.
   
   
(Oxford English Dictionary)
moom pitcher, n.
Etymology: Representing a colloquial pronunciation of moving picture n. Compare earlier pitcher n.4
colloq. (orig. and chiefly U.S.).
1929   W. Winchell in J. P. McEvoy Hollywood Girl xv. 232   Jimmy Doyle, back on the Evening Tab after a short parole in Times Square and Hollywood, and Betty Byrne, moom pitcher gel on same rag, are That Way.
1938   R. Franken Gold Pennies xviii. 209   The sale of the book has nothing to do with the thousand a week. That’s the salary you’re being offered to write for the moom-pitchers.
       
Google Books
Hearst’s International
Volume 44  
1923
Pg. 147:
“A soft-livin’ lad like him dat’ll go to woik in a foundry is a hero an’ he’d oughta be starred in moom-pitchers.”
 
11 March 1928, New York (NY) Times, “Out of the West,” sec. 10, pg. 2, col. 6:
With what the unsparing realist, Walter Winchell, calls the moom pitchers holding forth in all their magnificence in Hollywood, Los Angeles boasts a colony of those who produce what passes for literature.
 
14 March 1928, Variety, pg. 17 ad:
Louie: “Somebody’s wisin’ that moom pitcher crowd up to your gags which ain’t so good for us, if you ast Little Louie.”
(For the movie Dressed to Kill.—ed.)
 
10 June 1928, New York (NY) Herald Tribune, “The State Film Censor Talks About Duties of His Office” by Marguerite Tazelaar, sec. 7, pg. 3, col. 7:
IN THE hands of an up-state schoolmaster lies the power to make or break New York’s “moom pichers.”
 
9 August 1928, Life magazine, “Along the Main Stem” by Walter Winchell. pg. 16, cols. 2-3:
It took the good old moom picture industry to get that turkey’s number.
 
6 September 1928, Life magazine, “Along the Main Stem” by Walter Winchell, pg. 15, col. 2:
Ben Lyon, the moom picture actor, recites it: “Thirty days hath September, April, June and a week-end in Hollywood.”
 
16 November 1971, Philadelphia (PA) Daily News, “Winchell” by Bob Thomas, pg. 36, col. 1:
Moom picture, flicker,
Phlicker  (moving picture)
     
Google Books
Winchell, His Life and Times
By Herman Klurfeld
New York, NY: Praeger
1976
Pg. 58:
In 1931, Scribner’s magazine listed several “Winchell words”: “Dotter: Daughter…Moom Picture: Moving Picture…”
 
Google Books
Winchell:
Gossip, Power and the Culture of Celebrity
By Neal Gabler
New York, NY: Vintage
1995, ©1994
Pg. XII:
Movies were “moom pitchers” and movie lovers were “cinemaddicts.”