This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
濚 combines 氵 (water) with 榮, which likely contributes the sound. The exact historical development is uncertain.
The water radical 氵 beside 榮 suggests something related to water, but the exact meaning is unclear. Picture a small stream (おがわ) flowing beside a flourishing tree (榮).
For エイ, imagine an 'A' grade stream: the letter 'A' sounds like エイ, and the stream is the best (A-grade) water.