school of fish, fish's mouth moving, exhaling sound
哈 centers on the sound and motion of exhaling or gaping, especially as seen in a fish's mouth opening and closing. The 'school of fish' sense likely extends from the image of many mouths moving together.
哈 combines 口 (mouth) with 合, which likely contributes both sound and the idea of joining or fitting together, suggesting mouths opening and closing in unison. The exact historical development is uncertain.
A mouth 口 beside 合 (fit/join) suggests many mouths moving together, like a school of fish gaping and exhaling in rhythm.
For ゴウ, imagine a fish going 'gou-gou' as it exhales: the sound 'gou' cues ゴウ while the fish's mouth opens and closes.
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