Green’s Dictionary of Slang

certainly! really! absolutely!

[1866		J. Greenwood Little Ragamuffin 325: ‘’Tain’t so disappointin’ as yer thought it would be; is it, Rip?’ ‘Not a half.’].
1902		A.N. Lyons Hookey 33: Wotcher! ’Oo’s got the perlice in their shop? ’Ookey Walker? Not ’arf!
1912		E. Pugh City Of The World 259: ‘And it was this man – this Manders —?’ ‘Not half, it wasn’t.’.
1913		Truth (Sydney) 27 Apr. 11/3: When so how he’d rap about it, / Sayin’ it was crook — not harf.
1916		N. Douglas London Street Games 37: Not ’arf.
1922		‘Sapper’ Black Gang 378: ‘A bomb outrage?’ [...] ‘Not ’arf, guv’nor.’.
1927		Brisbane Courier 20 Aug. 23/7: Strike me pink, if anyone'd call them blokes ‘glorious’ they would have sworn at ’em - not ’arf!'.
1938		J. Curtis They Drive by Night 77: ‘’Tain’t half cold,’ said Shorty. ‘Not half.’.
1942		Whizzbang Comics 55: Not half he isn’t!
1947		S. Lewis Kingsblood Royal (2001) 214: ‘Not half!’ said Vestal, who had been eavesdropping on the extension phone.
1959		F. Norman Fings I i: Not arf, I don’t fink.
1976		P. Theroux Family Arsenal 86: He said, ‘Not half.’.
1984		‘Derek Raymond’ He Died with His Eyes Open 32: ‘Heavy drinker, was he?’ ‘Whew! Heavy? What, him? Not half!’.
1999		K. Sampson Powder 6: It was difficult to keep a critical distance (not half!).
2024		J. Meades Empty Wigs (t/s) 520: Tamara wrote in English and translated herself into Flemish and French. Daunting? ‘I’ll say! Not ‘arf!’.