“BOSS spelled backwards is double-SOB” (“SOB” is “son of a bitch”) is a humorous one-line saying that has been cited in print since at least 1957. Reader’s Digest credited Al Deeming for the line in 1958, but it’s not clear who Al Deeming is or when he said it.
 
“Built On Self Success” (a backronym or back acronym) is another take on the word “boss.”
 
   
Google Books
Petroleum Engineer for Management
Volume 29
1957
Pg. E21:
BOSS, spelled backwards is double SOB.
   
Google Books
Treasury of Wit & Humor
Pleasantville, NY: Reader’s Digest Association
1958
Pg. 62:
ONE MAN to another: “He’s a boss spelled backward — you know: double S.O.B.” — Al Deeming
 
8 May 1959, Amarillo (TX) Globe-Times, pg. 2, col. 6:
Barry asserted he had been called “double SOB.” “That’s simply BOSS spelled backwards,” smiled Barry.
     
Google Books
Typo Graphic
1960
Pg. 511:
He’s a boss spelled backwards . . . a double s.o.b.
 
26 October 1966, Altoona (PA) Mirror, pg. 10, col. 2:
He (Milton Shapp—ed.) tells union groups: “Always remember that boss spelled backwards is double SOB.”
 
Google Books
The Giant Book of Insults:
Incorporating 2000 insults for all occasions and 2000 more insults
By Louis A. Safian
Secaucus, NJ: Citadel Press
1967
Pg. 142:
He’s a boss spelled backwards— double s.o.b.
 
17 July 1969, Press-Telegram (Long Beach, CA), Earl Wilson entertainment column, pg. A26, col. 3:
An actor complained about a difficult director: “He’s a boss, spelled backwards. You know—double s, o, b.”
 
Google News Archive
27 July 1970, Sarasota (FL) Herald-Tribune, “It Happened Last Night” by Earl Wilson, pg. 7B, col. 2:
Bosses Week is going to be observed Oct. 14 and the secretaries think their wonderful employers deserve a week of honoring themselves. And they reminded me that BOSS is double SOB spelled backwards.
 
Google News Archive
4 June 1974, The Ledger (Lakeland, FL), “If You Want To Be A Millionaire” by James E. Davis, pg. 6A, col. 3:
See that your employes don’t refer to you as the boss spelled backwards—double SOB!
   
Santa Paula (CA) Times
Rey Frutos, Jim Garfield, Jim McCoy, Dan Robles and Jim Tovias honored, really roasted
By Peggy Kelly
Santa Paula News
Published:  November 02, 2001
(...)
It’s not that Jim McCoy is a bad boss, said Ron Merson, but “you know what boss spelled backwards is. . .double SOB!”
 
Google Books
Microeconomics for MBAs:
The Economic Way of Thinking for Managers
By Richard B. McKenzie and Dwight R. Lee
New York, NY: Cambridge University Press
2006
Pg. 153:
Bosses are also the butts of much humor. There is the old quip that boss spelled backward is “Double SOB.”
   
Austin (TX) Chronicle
The Hightower Report
Bad Bosses; and a Bill to Ban Sweatshop Labor
BY JIM HIGHTOWER, FRI., AUG. 25, 2006
(...)
Indeed, it’s probably no coincidence that “boss,” spelled backward, is double-sob.