This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
蘡 combines 艹 (grass) with 嬰, which likely contributes sound. The exact historical development is uncertain.
The top 艹 suggests a plant, and the bottom 嬰 is a complex shape. Picture a rare, mysterious plant whose name is uncertain.
For オウ, imagine saying 'Oh!' when you see this rare plant: Oh -> オウ.
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