miasma
瘴 centers on a harmful, oppressive vapor or atmosphere: a miasma, the kind of foul air believed to cause disease in swampy or tropical regions.
瘴 combines the sickness radical 疒 with 章, which likely provides the sound (ショウ) and may also hint at a spreading or pervasive quality, as miasma was thought to be a disease-causing vapor that spreads through the air.
The sickness enclosure 疒 surrounds 章, which looks like a badge or emblem. Imagine a foul, disease-laden mist rising from a swamp, clinging to everything like a sickening badge of decay.
For ショウ, picture a show (ショウ) of eerie swamp gas rising from the sickness enclosure: the show of miasma cues ショウ.
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