This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
胘 combines the flesh component ⺼ with 玄, but the exact historical development is uncertain.
The left side ⺼ suggests flesh or body, and the right side 玄 suggests dark or mysterious. Imagine a mysterious body part whose function is unknown.
For ケン, imagine a mysterious body part that only Ken can identify: Ken -> ケン.