millipede
蚰 centers on a specific many-legged creature: the millipede. It is a narrow, concrete term for this insect-like animal.
蚰 combines 虫 (insect) with 由, which likely provides the sound. The character was created to name a specific insect, the millipede.
The insect radical 虫 on the left and 由 on the right together suggest a creeping bug: picture a millipede winding through a rice field (由 looks like a field with a path).
For ユウ, imagine a millipede crawling slowly, and you say 'yuu' (like 'you') as you point at it: you -> ユウ.
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