millet
穈 centers on millet, a type of grain. The meaning is specific to this crop.
穈 combines 麻 (hemp) and 禾 (grain), likely indicating a grain plant similar to hemp or used in a related context. The exact historical development is uncertain.
Outside is 麻 (hemp), inside is 禾 (grain). Picture a field where millet grows among hemp plants, the grain heads looking like tiny versions of the hemp leaves.
For ボン, imagine a bonfire where millet stalks are burned after harvest: bon -> ボン, and the millet crackles in the flames.
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