The shrub crowberry, Empetrum nigrum; (also) the berries, or a berry, of this plant.
Origin
Mid 19th century; earliest use found in Phytologist. Probably from knop + wort, perhaps influenced in form by Scots (north-eastern) croupert (also kraupert, crowpert), in the same sense; compare also Scots (north-eastern) croupans (also croupens) crowberry. With the formation compare Danish knopurt knapweed (from knop + urt).