This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 呄 is uncertain. It visually combines 乃 and 古, but no clear etymological explanation is available.
With no clear meaning, picture the top 乃 as a bent figure and the bottom 古 as something old. Together they suggest something ancient and obscure, but its meaning remains a mystery.
For コク, imagine an old, mysterious object that makes a knocking sound: knock -> コク, echoing from the ancient shape of 呄.
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