monme, 3.75 grams, (kokuji)
匁 is a Japanese-made unit of weight, specifically the monme (about 3.75 grams). It has no abstract or extended meanings beyond this measurement.
匁 is a kokuji (Japanese-made character) created by combining 勹 (wrapping) and 乂 (a stylized form suggesting a weight or measure). It was devised to represent the monme unit.
Picture a wrapping cloth 勹 tied around a small weight 乂: this bundle is exactly one monme.
For もんめ, imagine a merchant saying 'one monme' while wrapping the weight: the whole phrase 'monme' cues もんめ directly.
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