This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
磤 combines 石 (stone) with 殷, which likely contributes the sound. The exact historical development is uncertain.
The stone radical 石 beside 殷 suggests something related to stone, but the meaning is unclear. Picture a mysterious inscribed stone whose purpose is unknown.
For イン, imagine an inn built from the mysterious stone: inn -> イン, and the stone 磤 marks the entrance.
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