foolish, silly, stupid, an imbecile
傻 centers on a lack of intelligence or good judgment: being foolish, silly, or stupid. The meaning extends naturally to a person who is an imbecile.
傻 is a phono-semantic compound with 亻 (person) and a phonetic element that historically contributed the sound. The exact origin of the right side is uncertain, but it likely depicted something related to foolishness or simplicity.
A person 亻 with a tangled, silly-looking right side: imagine someone whose thoughts are as jumbled as the strokes, making them foolish.
For サ, picture a silly person saying 'sah' instead of a smart word: sah -> サ, and their foolishness is clear.
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