Green’s Dictionary of Slang

1. (UK/US) a drink.

1859		C.J. Lever Davenport Dunn 224: There, ‘liquor up,’ as the Yankees say, cried Davis, passing the decanter towards him.
1861		R.F. Burton City of the Saints 356: After [...] a last ‘liquor-up’.
1873		F. Boyle To Cape for Diamonds 273: With many a ‘liquor-up,’ and many a joke [...] we wended our way.
1889–90		Barrère & Leland Dict. of Sl., Jargon and Cant.
1895		Mirror of Life 9 Mar. 10/4: After a ‘liquor up’ and a talk about things in general, Jem got the old ’un an order for the play for himself and friends.

2. a drinking spree; a party.

1899

C. Rook Hooligan Nights 106: There was a rare old liquor up at that pub.