The quality or state of being foolish, stupid, or lacking intelligence; having a slow or dull mind.
From 'dimwit' (dim + wit), combining Old English 'dim' (faint, obscure) and 'wit' (intelligence, mental sharpness). The suffix '-ness' converts the adjective to a noun. First recorded in early 20th century.
The term 'dimwit' became popular slang precisely when electric lighting was transforming homes—making 'dim' a vivid insult for unclear thinking. Language often borrows from sensory experiences to describe mental states.
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