This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
衃 combines 血 (blood) and 不 (not), but the historical origin and original meaning are uncertain. It may have been a phono-semantic compound, but the exact development is unclear.
With 血 (blood) and 不 (not), picture a situation where blood is not flowing properly, but since the meaning is uncertain, treat this as a visual placeholder.
For ハイ, imagine a high-pitched cry when blood is not clotting: high -> ハイ, tied to the blood component.
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