Green’s Dictionary of Slang

1. of a villain, ready for any criminal undertaking.

a.1790		H.T. Potter New Dict. Cant (1795).
1809		G. Andrewes Dict. Sl. and Cant.
1823		‘Jon Bee’ A Dict. of the Turf, The Ring, The Chase, etc.
1835		G. Kent Modern Flash Dict. 3: All set – desperate fellows, ready for any kind of mischief.
1848		Flash Dict. in Sinks of London Laid Open.

2. ready, prepared.

1844		J. Gregg Commerce of Prairies I 54: Each teamster vies with his fellow [...] and it is a matter of boastful pride to be the first to cry out — ‘All’s set!’ [DA].
1917		R. Lardner Gullible’s Travels 90: ‘We’re all set.’ ‘No, we’re not,’ she says. ‘That just fixes me.’.
1929		E. Booth Stealing Through Life 300: ‘All set, Bill,’ I called to Dan.
1939		R. Chandler ‘Trouble Is My Business’ in Spanish Blood (1946) 207: ‘We’ll have to leave now.’ ‘All set.’.
1948		(con. 1944) N. Mailer Naked and Dead 13: You’re all set for everything now.
1958		F. Norman Bang To Rights 28: My door was unlocked my shoes had already been taken away from me, so I was all set.
1964		P. White Burnt Ones 15: ‘All set?’ Ossie asked.
1979		Fantastic Four Annual 31: Okay, lads – all set?
1981		J. Ellroy Brown’s Requiem 33: She tore out and I was all set for hot pursuit.