髀 combines 骨 (bone) with 卑, which likely contributes the sound and may relate to the lower body. The character specifically denotes the thigh bone or thigh.
Meaning mnemonic
The left side 骨 means bone, and the right side 卑 suggests something low or base. Picture the thigh bone as the sturdy base bone of the leg.
Reading mnemonic
For ヒ, imagine a thigh bone being used as a simple tool to heave something heavy: heave -> ヒ, and the bone does the lifting.
