scupper, n. — Green’s Dictionary of Slang

scupper n.

[? SE scupper, a boat’s drain through which dirty water can run]

a prostitute.

1935		A.J. Pollock Und. Speaks n.p.: Scupper, a prostitute.
1944		P. Kendall Dict. Service Sl. n.p.: scupper [...] a lady of easy virtue.
1966		Trimble 5000 Adult Sex Words and Phrases.
1970		G. Greer Female Eunuch 265: More familiar terms in current usage refer to women as receptacles for refuse, [...] as tramp, scow, scupper.