Green’s Dictionary of Slang

(US prison) to surrender, to act in a cowardly manner.

1991		Cooper & Wright New Jack City [film script] Nino, please! Don’t start bitching up. You don’t have my product or my money.
2000		Other Side of the Wall: Prisoner’s Dict. July 🌐 Bitch Up: Chicken out or be a coward. (FL) [...] To cry or give in. (NY).
2006		Prison Slang Mommyblogger mydogharriet.blogspot.com 2 Mar. 🌐 Take it to the square if you need to. Make him bitch up. Don’t be afraid to be a toosh-hog.
2023		Rayman & Blau Riker’s 86: They think, ‘Oh, there’s a white guy in there. Oh, he’s going to bitch up right away to us’.