Resembling or characteristic of a booby; foolish, silly, stupid, or clumsy in behavior or appearance.
From 'booby' plus the adjective-forming suffix '-ish' (Old English '-isc'). The suffix creates an adjective meaning 'of the nature of' or 'somewhat like' the root word.
The suffix '-ish' is incredibly productive in English—we use it to soften and modify meanings, turning nouns into adjectives: bookish, foolish, boobish. It's like adding a degree of similarity!
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