Superlative form of croupy; most affected by, characterized by, or resembling croup (the respiratory condition).
From croupy (adjective form of croup, the respiratory disease) + -est (superlative suffix). Croup itself may derive from Scottish 'croup' or 'kroup,' possibly imitative of the harsh sound.
Croup has one of the most distinctive sounds in medicine—that harsh, barking 'croup' cough—so 'croupiest' captures which sick child sounds most like a troubled seal!
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