ant, leech
螞 centers on small crawling or parasitic creatures: ants and leeches. Both are tiny animals that can appear in large numbers or attach themselves persistently.
螞 combines 虫 (insect) with 馬 (horse), likely as a phono-semantic compound where 馬 contributes the sound and 虫 indicates a small creature. The exact historical development is uncertain.
An insect 虫 as big and stubborn as a horse 馬: imagine a giant ant or leech with the tenacity of a horse, impossible to shake off.
For バ, picture a leech shaped like a bar of soap, clinging to a horse: bar -> バ, and the insect 虫 on the horse 馬 is that stubborn leech.
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