This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
娎 combines 折 (top) and 女 (bottom). The exact historical development is uncertain, and the character is rare in modern Japanese.
The top 折 suggests breaking or folding, and the bottom 女 is a woman. Without a clear meaning, picture a woman carefully folding something, but the intended idea remains unclear.
For ケツ, imagine a woman folding a piece of cloth and making a sharp crease with a 'kets' sound: kets -> ケツ.