astragalus n.

1540s in botany, a large genus of plants that include the milkvetch, loco-weed and goat's thorn; 1560s in anatomy in reference to a type of bone, usually in or near the ankle. Historically these bones, especially those taken from deer, were used as a type of die for games and fortune telling. It is attested from 1560s in architecture as a type of molding. All senses are from Greek astragalos "neck vertebra; ankle bone; knuckle-bones (used as dice)," which generally is considered to be from the same root as osteon "a bone" (see osteo-), but Beekes says they are unrelated.