Meaning

noun common perennial aromatic herb native to Eurasia having buttonlike yellow flower heads and bitter-tasting pinnate leaves sometimes used medicinally

originInherited from Middle English tansy, tansey, syncopic forms of earlier tanesie, tanesei, from Old French tanesie, tanoisie, tanasie, tanaisie, from Medieval Latin tanacetum, atanacetum, attested since the 8th century, of obscure origin, speculated from Ancient Greek ἀθανασία (athanasía, “immortality”) owing to hallucinations from the thujone in the plant, else from taenia (“tapeworm”) due to its…

Etymology from Wiktionary, CC BY-SA 3.0