cry
呱 centers on the sound of crying, especially the wail of a newborn. It is a specific vocal expression rather than a broad emotional state.
呱 combines 口 (mouth) with 瓜, which likely acts as a phonetic component. The character is used to represent the sound of crying, especially an infant's first cry.
A mouth 口 beside a melon 瓜: imagine a baby's mouth opening wide like a round melon as it lets out a loud cry.
For コ, picture a crying baby whose wail sounds like 'ko, ko!' The mouth 口 and the round melon 瓜 shape together suggest the round 'ko' sound.
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