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"region of the body between the anus and the genital organs" (jocularly called a taint), early 15c., from Medieval Latin perinaeon, Late Latin perineum, from Greek perinaion, perinaios, from peri- "near" (see peri-) + inan "to carry off by evacuation," of unknown origin.
perineum per·i·ne·um (pěr'ə-nē'əm)
n. pl. per·i·ne·a (-nē'ə)
The portion of the body in the pelvis occupied by urogenital passages and the rectum, bounded in front by the pubic arch, in the back by the coccyx, and laterally by part of the hipbone.
The region between the scrotum and the anus in males, and between the posterior vulva junction and the anus in females.