Green’s Dictionary of Slang

nearly, almost.

1848		G.F. Ruxton Life in the Far West (1849) 31: ‘How do you feel?’ ‘Half froze for hair. Wagh!’.
1867		‘Artemus Ward’ Artemus Ward in London in Complete Works (1922) 498: Yet plain don’t half express my looks.
1869		T. Taylor New Men & Old Acres 11: Ber: If I were to take your advice, I’m sure you wouldn’t half like it!
1885		Bulletin (Sydney) 23 May 18/1: ‘Tas,’ who is daily implored in the agony column of the Sydney Herald to return home, because the baby is sick, doesn’t seem to have turned up yet. Her people aren’t half smart. Let them put this in:- ‘Tas. Come home immediately. Kind lady has adopted baby without a premium.’ That would send her back [...].
1903		A.H. Lewis Boss 316: I don’t half like it.
1918		C.J. Dennis ‘West’ in Chisholm (1951) 97: Said ’e. ‘Now, dinkum, talkin’ square, / When you git gazin’ over there / Don’t you ’arf want to cry?’.
1920		R.J. Fry Salvation of Jemmy Sl. II i: Yer father, Ig, has been trying for twenty years to get in with them folks an’ here you do it without half trying.
1922		‘J.H. Ross’ Mint (1955) 36: [ref. to trainee airmen] You bloody swaddies can’t half yaffle.
1956		Shelagh Delaney A Taste of Honey 41: You don’t half knock me about.
2004		Alan Coren Omnibus 91: ‘He don’t half come out with ’em,’ said the bulldog, ‘for something that looks like a sink tidy.’.