gorilla, n.² — Green’s Dictionary of Slang

gorilla n.²

[SE gorilla, i.e. the size of the primate, a huge monkey n. (12a)]

(US drugs) a severe heroin addiction (cf. gorilla adj. (2)).

1956		E. Hunter Second Ending 301: If you have a gorilla, I can guarantee that you will steal [...] you will do anything to feed that gorilla because he is the boss and not you.
1981		personal communication in Spears Sl. and Jargon of Drugs and Drink (1986).
1994		N. McCall Makes Me Wanna Holler (1995) 358: That shit [i.e. crack] will knock your socks off in a minute and put a go-rilla on your back.