mythological wingless dragon of
螣 refers to a mythological wingless dragon. The given meaning is incomplete, but the core idea is a specific legendary creature.
螣 combines 虫 (insect/reptile) with 朕, which likely contributes the sound. The exact historical development is uncertain, but it is a phono-semantic compound for a dragon-like creature.
The insect radical 虫 suggests a creeping creature, and the right side looks like a complex mythical beast. Imagine a wingless dragon slithering like a snake.
For トウ, picture a toe of the dragon: toe -> トウ, and the dragon's toe is wingless but powerful.