Green’s Dictionary of Slang

(US black) the anus.

1969		H. Rap Brown Die Nigger Die! 27: The hard hitter the bullshitter the poly-nussy getter / The beast from the East the Judge the sludge / The women’s pet the men’s fret and the punks’ pin-up boy.
2000		Ebonics Primer at www.dolemite.com 🌐 sludge Definition: when a ho wants the big d through the back door Example: I don’t want it there homey, I want in my sludge!