Green’s Dictionary of Slang

1. the winning throw at dice.

1708		M. Prior Cupid and Ganymede in Works (1959) I 273: Cries ganymede: The usual Trick: Seven, slur a Six; Eleven: A Nick.
1772		Bridges Burlesque Homer (3rd edn) 288: Out pops the dice, cries nestor — Seven / ’S the main; a nick, by Jove, eleven.
1797		Bridges Burlesque Homer (4th edn) II 25: [as cit. 1772].
1825		C.M. Westmacott Eng. Spy I 270: Ay, that I will, I’ll hit the nick.
1832		Satirist (London) 22 Jan. 31/1: If the caster calls 7, and throws 7 or 11, he wins, as both 7 and 11 are nicks to 7; and if he calls either 5,6, 8, or 9, and throws what he calls, it is called a nick, and he wins.
1853		Bell’s Life in Sydney 11 June 2/7: ‘A nick,’ exclaimed Inspector James Singleton, as he rushed into the room.

2. as the nick, the proper thing, the fashionable thing, the best of health.

1788		R. Seymour Murray’s Mag. I 472: The word Ton is quite abolished. Everything that is fashionable is now called the Nick. The fashionable Ribbons and Gauzes are Polignac and Jofilé.
c.1864		‘The Squire’s Thingumbob’ Rakish Rhymer (1917) 83: His thingumbob, it stood so stiff, ’twas really in the nick, sirs.
1879		‘’Arry on Crutches’ Punch 3 May 201/1: Toppers in sticks; / They do give a chap sech a hair [...] when they’re up to the nicks.
1883		‘’Arry at the Royal Evening Fête’ Punch 28 July 38/2: Arf-a-crown for the tipple was stiff, but the feeling, my boy, there’s the nick!
1890		‘’Arry on [...] the Glorious Twelfth’ Punch 30 Aug. 97/2: There’s the nick o’ the matter, he reason of all this un-English wild chat.

3. (UK und.) an opportunity.

1829

Morn. Advertiser (London) 5 Nov. 4/3: His companion told him that was now a prime ‘nick’ for a piece of ‘squeeze’. Mr Wyatt — ‘What do you mean?’ [...] ‘They are flash terms, Sir. — “Nick” means opportunity and “squeeze” signifies silk.