This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
渶 combines 氵 (water) with 英, which likely contributes the sound. The exact historical development is uncertain.
The water radical 氵 beside 英 suggests a name or place related to water, but the meaning is unclear.
For エイ, imagine the English letter 'A' floating on the water: 'A' -> エイ, and the water radical 氵 keeps it afloat.
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