Having a head shaped like an egg, or figuratively, being absent-minded or foolish despite appearing intellectual.
From 'egg' + 'headed', likely originating in the early 20th century as slang to describe someone with a round, smooth head or as a mocking term for intellectuals.
The term 'egghead' became American slang in the 1950s to mock intellectuals and academics, yet it also appeared positively in phrases; the ambiguity shows how society struggles with the value of pure intellect.
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