dirty
骯 centers on filth and impurity, describing something that is physically or morally dirty.
骯 combines 骨 (bone) with 亢, which likely contributes the sound. The exact historical development is uncertain, but the character is used to express dirtiness.
Bones 骨 piled up with a high, protruding shape 亢 suggest a messy, dirty heap. Picture a pile of dirty bones that no one has cleaned.
For コウ, imagine a dirty coat hanging on a bone: coat -> コウ, and the coat is filthy like the meaning of 骯.
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