wasp
螉 refers to a wasp, a stinging insect.
螉 combines the insect radical 虫 with the phonetic component 翁, which likely indicates the sound. The exact historical development is uncertain.
The insect radical 虫 on the left suggests a bug, and the right side 翁 looks like a plump body with wings. Imagine a wasp with a rounded, old-man-like shape buzzing around.
For オ, picture an old man (翁) swatting at a wasp while shouting 'Oh!' in surprise: Oh -> オ.
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