A mischievous child, especially a poor or street child; also, a spiky sea creature with a round body called a sea urchin.
From Old French 'urchon' which came from Latin 'ericius' meaning hedgehog. The word was applied to street children because they were seen as prickly, difficult, and hard to control—just like the spiky animal.
Medieval people called troublemaking street kids 'urchins' because they compared them to hedgehogs—prickly, defensive, and living on the edges of society. Then the name stuck to actual sea urchins, and we almost forgot the original insult!
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