Green’s Dictionary of Slang

drap n.

[var. on colloq. drab]

a ‘nasty, sluttish whore’ (Egan’s Grose).

‘Letter from a Missionary Bawd’ in Carpenter Verse in English from Tudor & Stuart Eng. (2003) 427: McDonnels house [i.e. brothel] does hinder much my trade, / For all the Irish draps do there parade.
[UK] Egan Grose’s Classical Dict. of the Vulgar Tongue.