flight of a dragon, dragons moving
龖 centers on the image of dragons in motion, specifically a pair of dragons flying or moving together. The given meanings describe this as a flight or movement of dragons.
龖 is formed by doubling the dragon character 龍, likely to emphasize the idea of multiple dragons or a pair of dragons in motion. The exact historical origin is uncertain, but the duplication is a common way to intensify or pluralize a concept.
Two dragons 龍 side by side, moving together through the sky. Their paired flight is the core image of 龖.
For トウ, imagine the two dragons flying in a tight formation, like a tow rope pulling them together: tow -> トウ, and the dragons move as one.