Plural of cuckoo; a family of birds known for their distinctive calls and for laying eggs in other birds' nests; also, plural of cuckoo meaning deceived husbands or foolish people.
From Old English 'cuc' (imitative of the bird's call). The metaphorical senses developed because the bird's behavior (laying eggs in other nests) made it a symbol of deception and foolishness.
Cuckoo birds are some of nature's most successful con artists—they've perfected mimicry so well that host birds can't tell the difference, and their 'cuckoo' call is so iconic it inspired clocks, insults, and even a Beatle's album title.
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