Green’s Dictionary of Slang

1. a fool, a worthless person.

1858		W. Pratt Ten Nights in a Bar-Room II i: Oh, you git, with your story-book talk!
1941		G. Kersh They Die with Their Boots Clean 125: Don’t be such a silly Git, Bullock!
1956		‘Charles Raven’ Und. Nights 18: Tryin’ to shop us, eh, you four-eyed git!
1966		T. Keyes All Night Stand 189: ‘I haven’t got the bread.’ [...] ‘Course you have, you half-arsed git.’.
1977		S. Berkoff East in Decadence and Other Plays (1985) 55: Those long-nosed gits, those evil-smelling greasy kikes had barricades up.
1983		A. Payne ‘Get Daley!’ Minder [TV script] 25: Get knotted, you Welsh git.
1990		R.G. Barratt ‘Real Men Save Whales’ in What Do You Reckon (1997) [ebook] I can dig members of the National Party [...] calling all environmentalists long-haired gits.
1992		I. Rankin Strip Jack 176: Why not? Because he’s an oily git’s why not.
2000		Guardian Weekend 22 Jan. 69: It’s a sign that I’m a sad old git.
2008		(ref. to 1971) F. Dennis ‘Old Bailey’ Homeless in my Heart 179: I see these poncey gits [...] have got / Just what they fuckin deserve.

2. (N.Z. prison) a member of the Mongrel Mob [specific use of sense 1 + elision of ‘dog shit’].

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 78/1: git n. a member of the Mongrel Mob.