Green’s Dictionary of Slang

doxy n.

also doccy, doxey, doxie
[? Du. docke, a doll or SE dock, an animal’s tail; Ribton-Turner, A History of Vagrants (1887), suggests Lowland Scot. doxie, lazy]
(UK Und.)

1. [early 16C–mid-19C] the female companion of a variety of mendicant villains; spec. a young woman, or an unattached woman, older than a dell n. (1) and younger than a mort n. (1)

2. [early 16C+] a general term, usu. derog., for a woman or girl, esp. a mistress.

3. [late 17C+] a prostitute.

In phrases

arch-doxy (n.) (also arch-doxey)

[early 18C–early 19C] (UK Und.) the woman accomplice of a gang-leader (cf. arch-dell under dell n.).

play doxy (v.)

of a man, to visit a brothel for sex.