marine crab
蛑 centers on a marine crab, a sea creature with a hard shell and claws.
蛑 combines 虫 (insect/creature) with 牟, which likely contributes the sound. The exact historical development is uncertain, but the structure suggests a phono-semantic compound for a type of crab.
The insect radical 虫 on the left hints at a small creature, and the right side 牟 looks like a crab's body with legs. Together they form a marine crab.
For ボウ, imagine a crab crawling along the ocean floor with a bow-legged walk: bow -> ボウ, and the crab's sideways scuttle matches the sound.
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