newt, turban shell
蠑 centers on a specific small creature: a newt, and by extension a turban shell, likely due to a perceived visual or categorical similarity in traditional classification.
蠑 combines 虫 (insect/creature) with 榮, which likely provides the sound エイ. The exact historical development is uncertain, but it follows a common phono-semantic pattern for animal names.
The left side 虫 signals a small creature. The right side 榮 looks like a complex shell or a curled amphibian. Picture a newt crawling out of an ornate turban shell.
For エイ, imagine the newt making a tiny 'eh!' sound as it slips on a wet rock: 'eh!' -> エイ.
—