Black as sipe (sype sp?)'s ass

Does anyone know the meaning and the origin of "black as sipe (sype sp?)'s ass"

Sipe, or its variant, sype, is a rather rare word, if also an old one. It means water percolating through the soil, or which has so percolated. It usually is pronounced to rhyme with pipe, but as sype-water in the southern U.S. it rhymes with peep.

I have never heard or seen the expression you inquire about.
SS