This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 腗 is uncertain. It combines the flesh radical ⺼ with 畁, but the origin and original meaning are unclear.
With no clear meaning, focus on the shape: flesh ⺼ beside 畁, which looks like a field 田 with extra strokes. Imagine a rare body part named after a field.
For ヒ, picture a single he (ヒ) standing in a field, pointing at the mysterious flesh part: he -> ヒ.