costmary

A Eurasian perennial herb (Chrysanthemum balsamita) in the composite family, having aromatic foliage sometimes used for potpourri, tea, or flavoring.

[Middle English costmarie : cost, costmary (from Old English, from Latin costum, from Greek kostos, from Sanskrit kuṣṭhaḥ) + marie, Mary, the mother of Jesus.]

An herb belonging to the composite plant family, which includes daisies, dandelions, marigolds and sunflowers. The silvery, fragrant costmary leaves have a minty, lemony character. They're used in salads, and as a flavoring in soups, veal and chicken dishes and sausages. Costmary is also called alecost (because it was used in making ale), Bible leaf (because its long leafs were used as book markers) and mint geranium.

The noun has 2 meanings:

Meaning #1: 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
  Synonyms: alecost, bible leaf, mint geranium, balsam herb, Tanacetum balsamita, Chrysanthemum balsamita

Meaning #2: leaves used sparingly (because of bitter overtones) in sauces and soups and stuffings