Green’s Dictionary of Slang

1. to a great (and unpleasant) extent.

1846		Swell’s Night Guide 65: ‘We charges a win for them slums, and a brown for the pawney.’ ‘Oh, that’s coming it stiff [...] Vy, thunder my posh.’.
1851		‘Billy Vite’ in Jolly Comic Songster 192: She fell stiff stone dead underneath the table.
1875		‘Aliph Cheem’ Lays of Ind (1905) 10: But none could touch the Major none could yarn so stiff as he.
1883		Nat. Police Gaz. (NY) 3 Nov. 6/2: ‘Give it [i.e. an act of extortion] him stiff’.
1885		Bulletin (Sydney) 28 Feb. 10/2: ‘By Jove, old man, you must have walked into the nectar divine pretty stiff last night! How much did you score on your own account?’ ‘Seven bottles.’.
1890		Sporting Times 29 Mar. 2/4: The North-American Indian (I have reason to know) can mix it uncommonly stiff.
1903		A.H. Lewis Boss 272: He hits up th’ bottle pretty stiff.
1917		F. Packard Adventures of Jimmie Dale (1918) I ii: You’re going to get it pretty stiff, anyhow.
1958		A. King Mine Enemy Grows Older (1959) 77: I’m worried stiff.
1962		R. Hauser Homosexual Society 91: I was frightened stiff in case he would talk and give a description.
1970		‘Red’ Rudensky Gonif 76: We’re going to knock over a bank so stiff it’ll never get up.
1976		(con. 1940s) J. Wolveridge Ain’t it Grand 79: They were worried stiff.

2. (Aus.) in a deliberately uncompetitive manner.

1889		Dead Bird (Sydney) 27 July 8/4: ‘C—t, ain’t he a beauty. I say, vot price him on a horse vot y’vanted to run stiff’.
1895		Truth (Sydney) 24 Mar. 5/2: Running ‘Stiff’. One witness [...] made the astounding admission that horses were frequently run ‘stiff’ at Randwick, adding that he had done it himself.
1914		Sport (Adelaide) 31 July 5/6: ‘Sport’ would like to know if Bert J. caught a ½d. sucker to run stiff in the football match at Koolunga.