millipede
蚿 centers on a specific many-legged creature: a millipede.
蚿 combines the insect radical 虫 with 玄, which likely contributes the sound. The exact historical development is uncertain.
The insect radical 虫 on the left tells you it's a bug, and the right side 玄 looks like a long body with many tiny legs, just like a millipede.
For ケン, picture a millipede named Ken with a thousand legs: Ken -> ケン, and the insect 虫 crawls by on all those legs.
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