Green’s Dictionary of Slang

(US prison) an unpleasant time in prison because of one’s personality, or crime (which may alienate other prisoners), or inability to adapt etc.

1967		P. Thomas Down These Mean Streets (1970) 321: I saw myself as I had been six years ago, hustling, whoring, and hating, heading toward the same long years and the hard bit.
1983		R. Klein Jailhouse Jargon and Street Sl. [unpub. ms.].
1997		(con. 1970s) G. Pelecanos King Suckerman (1998) 88: Those hard bits Ronald had to do later on.