Meaning

noun tansy-scented Eurasian perennial herb with buttonlike yellow flowers; used as potherb or salad green and sometimes for potpourri or tea or flavoring; sometimes placed in genus Chrysanthemum

noun leaves used sparingly (because of bitter overtones) in sauces and soups and stuffings

originFrom Latin costum, from Ancient Greek κόστος (kóstos, “an Oriental aromatic plant”), and Maria (“the Virgin Mary”); only indirectly related to English rosemary.

Etymology from Wiktionary, CC BY-SA 3.0