breathe on, yawn, roar
呴 centers on forceful or audible breath from the mouth: breathing onto something, yawning wide, or roaring loudly.
呴 combines 口 (mouth) with 句, which likely contributes the sound and may relate to breath or sound from the mouth. The exact historical development is uncertain.
The mouth 口 beside 句 suggests breath or sound coming out. Imagine a mouth breathing onto a cold window, yawning wide, or roaring like a lion.
For ク, picture a cool breath of air coming from the mouth: cool -> ク, and the breath fogs the glass.
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