Futomomo is a body part, the upper leg.

Japanese: 太腿 (ふともも)

“Momo” means thigh where “futo” is the adjective to mean fat, thick or large.

 

Futomomo shibari  (太腿縛り) : generally refers to a tie where the lower leg is tied to the upper leg

Futomomo zuri (太腿吊り):  Suspended from the futomomo tie.