Green’s Dictionary of Slang

(UK Und.) a low-ranking prostitute.

1860		Hotten Dict. of Modern Sl. etc. (2nd edn).
1889-90		Barrère & Leland Dict. Sl., Jargon & Cant I 267/1: common jack (army), low prostitutes are thus termed by the military in Woolwich, and probably in other garrison towns.