the.com/taint

means The small stretch of skin between the genitals and the anus, clinically called the perineum.

from "Taint" as slang is a clipped, half-joking shortening of the phrase "'taint this, 'taint that" (it ain't this, it ain't that) — a folk coinage playing on the idea that the spot isn't quite one thing or the other. It's unrelated to the older word "taint" meaning stain or corruption, which comes from Old French teint/teindre, "to dye or color," itself from Latin tingere. The anatomical slang and the dye-stain word just happen to collide in sound, not ancestry.