Green’s Dictionary of Slang

perkin n.

[? SE perry, a drink made from pears + dimin. sfx -kin]

weak cider; the washings from a cider barrel.

[UK]Grose Classical Dict. of the Vulgar Tongue n.p.: Perkin, water cyder.
[UK]Lex. Balatronicum.
[UK]Egan Grose’s Classical Dict. of the Vulgar Tongue.