calf (of leg)
腓 refers specifically to the calf of the leg, the fleshy back part below the knee.
腓 combines the flesh radical ⺼ (月) with 非, which likely contributes the sound. The character specifically denotes the calf muscle.
The flesh radical ⺼ on the left points to a body part, and the right side 非 looks like two rows of muscle fibers. Picture the calf muscle as a fleshy part with a striated appearance.
For ヒ, imagine a calf muscle so strong it can heave a heavy weight: heave -> ヒ, and the calf does the lifting.