nether region

Meanings

1. Hell; a realm beneath the surface of the earth conceived as the abode of the souls of the dead and, sometimes, as the abode of demons or evil spirits.
2. A place which is subterranean or enclosed beneath a surface, especially one which is dark, dank, or otherwise inhospitable.
3. The private parts between the legs; the groin or buttocks.

Etymology

From nether + region.