Green’s Dictionary of Slang

nip n.6

[SE nip, a portion of alcohol]

SE in slang uses

In compounds

nip joint (n.) [joint n. (3b)]

(US) an illegal drinking establishment where drink is sold in nips or small (orig. half-pint) measures.

Dly Press (Newport News, VA) 19 Mar. 10/4: [headline] Police Cracking Down on ‘Nip Joint’ Problem. Vice Squad detectives [...] have raided four of the so-called ‘nip joints’.
[US]P. Cornwell Hornet’s Nest 42: He [...] was bleeding from the fight he had gotten into at the nip joint where he had been gambling and drinking Night Train Express fortified wine.
[US]B. Bilger Noodling for Flatheads (2001) 100: There have always been two sorts of moonshine: the decent stuff, which is kept at home and sold to neighbors, and ‘nigger likker,’ [...] shipped to anonymous [...] nip joints in the big city.

In phrases

freshen the nip (v.)

to have a drink.

[Aus]Bell’s Life in Sydney 18 May 3/3: Bobby hastened to another grog shrine and ‘freshened’ the nip, with another bumper of Burton.