Green’s Dictionary of Slang

tuck up fair n.

the gallows.

1827		‘The Mill’ British Minstrel 111: The beaks have sent their traps arter ’em, and if they’re cotched, they’ll show ’em the fall of the leaf at Tuck-up Fair.
1835		G. Kent Modern Flash Dict. 34: Tuck up fair – Newgate, at a hanging time.
1840		G.W.M. Reynolds (trans.) V. Hugo Last Day of Condemned 39: He swore he’d make me dance on air, / To please the folks at Tuck-up fair.
1848		Flash Dict. in Sinks of London Laid Open [as cit. 1835].
1864, 1867, 1870		Hotten Sl. Dict. 262: Tuck-up-Fair the gallows. The notion of tucking up in connexion with hanging is derived from tucking up the bedclothes before going to sleep ― the last preparation.

In phrases

dangle at tuck up fair (v.)

to be hanged.

1835

‘Billy Bighead’ in Cove in Spedding & Watt (eds) Bawdy Songbooks (2011) IV 227: And ’twas by great good luck they say, / That he didn’t dangle at tuck-up fair.