crotch rope
A rope tied around the crotch area, used in sexual bondage (kinbaku/shibari).
When tying, the crotch rope must be tied with special care.
She gasped at the tightness of the crotch rope.
Compound of 股 (mata, 'crotch') and 縄 (nawa, 'rope'). The exact origin is uncertain, but it is a straightforward descriptive term used in the context of Japanese rope bondage.