Green’s Dictionary of Slang

(US) to ride in or drive a hackney coach or taxicab.

1879		Phila. Times 8 May n.p.: Are we more content to depend on street cars and walking, with the accustomed alternative of hacking at six times the money? [DA].
1903		Indep. 2 Apr. 771: I’ve been thirty-five years at the hackin’ business in Brooklyn and Manhattan [HDAS].
1939		J. Weidman What’s In It For Me? 111: Sure I know where it is. I’ve been hacking here in New York for—.
1949		N. Algren Man with the Golden Arm 318: I’ll drive cab [...] Hack all day ’n get a drum job nights.
1968		K. Brasselle Cannibals 142: I hacked in Vegas for five years.
1970		E. Tidyman Shaft 3: Maybe with hate from a life of hacking.
1976		P. Schrader Taxi Driver [film script] Personnel Officer: So whaddya want to hack for, Bickle? Travis Bickle: I can’t sleep nights.