Green’s Dictionary of Slang

to fill in for (on a job), to deputize for; in sport, to substitute for or to be substituted.

1853		‘Mark Twain’ letter 26 Oct. in Letters (1917) I 26: I am subbing at the ‘Inquirer’ office [DA].
1859		Wkly Varieties (Boston, MA) 29 Oct. 7/2: The Herald compositors, who allow him to ‘sub’ for them [...] to keep him out of the poorhouse.
1879		University Mag. Nov. 589: At Cincinnati where he [...] ‘subbed’ for the night men whenever he could obtain the privilege [DA].
1909		G.R. Chester Making of Bobby Burnit in DN IV:ii 142: Squiggs was subing for the day on the courts.
1912		S. Ford Trying Out Torchy 71: Uncle Rodney was explainin’ delicate how [...] I was goin' to sub for him to-night.
1935		H. McCoy They Shoot Horses, Don’t They? in Four Novels (1983) 8: I had about seven dollars I had made squirting soda in a drug store, subbing for a friend of mine.
1938		W. Winchell On Broadway 18 Mar. [synd. col.] Lyda Roberti subbed for the ailing Martya Raye (who went to a hosp).
1945		C. Himes If He Hollers 88: I subbed at end on the football team.
1952		W.R. Burnett Little Men, Big World 14: He was in a spot, subbing for Hardy.
1975		Spradley & Mann Cocktail Waitress 42: She called and said she wasn’t feeling well and asked me to sub for her.
1983		C. Heath A-Team 2 (1984) 140: Too bad you’re bound for the state pen or you might have been able to sub for Carson on the Tonight Show.
1997		Simon & Burns Corner (1998) 291: He subs himself back in, crashing the boards wildly.
2000		J.J. Connolly Layer Cake 63: What this needs is subbin out. We need to sub-contract it out.
2017		D. Winslow The Force [ebook] There’s no way we can sub the fake Monty for the real Monty in front of all those cops [...] who know him.