proper name
嫦 is a rare kanji used primarily as a proper name, with no clear standalone meaning. Treat its meaning as uncertain.
嫦 combines 女 (woman) with 常, which likely contributes the sound. The exact historical development is uncertain, and the character is mainly used in proper names.
A woman 女 beside the character 常, which suggests something constant or ordinary. As a proper name, it may evoke a woman of enduring presence.
For コウ, imagine a woman named 嫦 (Kou) who is always constant (常) in her habits: Kou -> コウ.
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Chang'e (Chinese goddess)