Junk (1940)

“[Al] Smith agrees with rival players that he hasn’t had much speed and says ‘I throw a bunch of junk.’” George Kirksey, UP, June 25, 1940. (Appeared in many papers.) 

Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1ST USE. 1949. “[Mickey] Haefner, noted for his knuckle ball, said he didn’t use much ‘junk’” (Associated Press dispatch on a one-hitter thrown by Washington Senators pitcher Haefner, May 11; Peter Tamony).