urchin (n.)

c. 1300, yrichon "hedgehog," from Old North French *irechon (cognate with Picard irechon, Walloon ireson, Hainaut hirchon), from Old French herichun "hedgehog" (Modern French hérisson), formed with diminutive suffix -on + Vulgar Latin *hericionem, from Latin ericius "hedgehog," enlarged form of er, originally *her, from PIE root *ghers- "to bristle" (source also of Greek kheros "hedgehog;" see horror).

Still used for "hedgehog" in non-standard speech in Cumbria, Yorkshire, Shropshire. Applied throughout 16c. to people whose appearance or behavior suggested hedgehogs, from hunchbacks (1520s) to goblins (1580s) to bad girls (1530s); meaning "poorly or raggedly clothed youngster" emerged 1550s, but was not in frequent use until after c. 1780. Sea urchin is recorded from 1590s (a 19c. Newfoundland name for them was whore's eggs); Johnson describes it as "a kind of crabfish that has prickles instead of feet."