ilium
Anatomical term for the uppermost and largest bone of the pelvis.
腸骨は骨盤の一部です。
The ilium is part of the pelvis.
iliococcygeus; iliococcygeal muscle
The term is composed of 腸 (intestines) and 骨 (bone), likely from the bone's proximity to the intestines. The exact historical derivation is uncertain.