This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
碽 combines 石 (stone) with 貢, which likely contributes sound. The exact historical development is uncertain.
The stone radical 石 suggests a connection to rocks or minerals, but the overall meaning is unclear.
For コウ, imagine a stone (石) being offered as tribute (貢), and the sound of the tribute is a deep 'koh' (コウ).
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