This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
峐 combines 山 (mountain) with 亥, which likely contributes a phonetic element. The exact historical development is uncertain.
The mountain radical 山 suggests a connection to mountains, but the overall meaning is unclear. Picture a mysterious mountain peak named with the sound 亥.
For カイ, imagine a mountain shaped like a giant 貝 (かい, shell): 貝 -> カイ, and the mountain is a rare shell-like peak.
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