Green’s Dictionary of Slang

sloop of war n.

a prostitute.

1859, 1860		Hotten Dict. of Modern Sl. etc.
1864, 1867, 1870		Hotten Sl. Dict.
1939		D. Maurer ‘Prostitutes and Criminal Argots’ in Lang. Und. (1981) 117/1: bladder. An unattractive prostitute. Also [...] sloop-of-war, swinging door, tabby, tart, tomato, each expressing varying degrees of unattractiveness.