vagina
腟 refers specifically to the vagina, a part of the female reproductive anatomy.
腟 is a phono-semantic compound: the flesh radical ⺼ indicates a body part, and 室 likely contributes the sound チツ. The exact historical development is uncertain.
The flesh radical ⺼ on the left marks this as a body part, and the right side 室 (room) suggests an inner chamber: think of the vagina as a bodily room.
For チツ, imagine a tiny room (室) inside the body that needs a key to enter: the key fits with a 'chitsu' click, cueing チツ.
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