vapour, steam
滊 centers on gaseous water: vapour or steam, the visible mist that rises from hot water.
滊 combines 氵 (water) with 氣 (vapour, gas), suggesting water in a gaseous state. The exact historical development is uncertain, but the component relationship is clear.
Water 氵 plus 氣 (vapour) gives water vapour: steam rising from a hot spring.
For キ, imagine a key made of steam that unlocks a hot bath: key -> キ, and the steam key fits the water vapour kanji.
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