Meaning

noun European strong-scented perennial herb with grey-green bitter-tasting leaves; an irritant similar to poison ivy

noun leaves sometimes used for flavoring fruit or claret cup but should be used with great caution: can cause irritation like poison ivy

noun sadness associated with some wrong done or some disappointment

originFrom Middle English rewe, reowe, from Old English hrēow (“sorrow, regret, penitence, repentance, penance”), from Proto-West Germanic *hreuwu (“pain, sadness, regret, repentance”). Cognates include German reuen (“to regret, to repent”) and Dutch rouwen (“to mourn, to grieve”). Probably ultimately from Proto-Indo-European *krows-. If so, note the same sense evolution with in this case cognate…

Etymology from Wiktionary, CC BY-SA 3.0