Green’s Dictionary of Slang

1. a guerilla.

1863

in R.G. Carter Four Brothers in Blue (1978) 2 June 277: Danger of being gobbled by gorills.

2. a thug [gorilla n.¹ (1)].

1931		D. Runyon ‘Blood Pressure’ in Runyon on Broadway (1954) 75: This Rusty Charley is what is called a gorill.
1940		J.H. O’Hara Pal Joey 49: I saw I was licked as those gorills do not care anything about law.