Japanese: 岩戸縄縛り
Iwato (岩戸): A mountainous place in Japan
  Iwa (岩) : Rock
Nawa (縄): Rope
Shibari (縛り): Tie

A tie where the models genitals are exposed by spreading the legs wide with ropes around the ankles and/or thighs.

The source for this name is found in the Japanese creation legend of sun goddess Amaterasu, where she is lured out of hiding (near a place called Iwato) and returned sunlight to Japan and the world.

See: History of Japan: Origin, History of Japan: Amaterasu