The Collaborative International Dictionary
Walnut \Wal"nut\, n. [OE. walnot, AS. wealh-hnutu a Welsh or foreign nut, a walnut; wealh foreign, strange, n., a Welshman, Celt (akin to OHG. Walh, properly, a Celt, from the name of a Celtic tribe, in L. Volcae) + hnutu a nut; akin to D. walnoot, G. walnuss, Icel. valhnot, Sw. valn["o]t, Dan valn["o]d. See Nut, and cf. Welsh.] (Bot.) The fruit or nut of any tree of the genus Juglans; also, the tree, and its timber. The seven or eight known species are all natives of the north temperate zone.
Note: In some parts of America, especially in New England, the name walnut is given to several species of hickory ( Carya), and their fruit.
Ash-leaved walnut, a tree ( Juglans fraxinifolia), native in Transcaucasia.
Black walnut, a North American tree ( Juglans nigra) valuable for its purplish brown wood, which is extensively used in cabinetwork and for gunstocks. The nuts are thick-shelled, and nearly globular.
English walnut, or European walnut, a tree ( Juglans regia), native of Asia from the Caucasus to Japan, valuable for its timber and for its excellent nuts, which are also called Madeira nuts.
Walnut brown, a deep warm brown color, like that of the heartwood of the black walnut.
Walnut oil, oil extracted from walnut meats. It is used in cooking, making soap, etc.
White walnut, a North American tree ( Juglans cinerea), bearing long, oval, thick-shelled, oily nuts, commonly called butternuts. See Butternut.
Butternut \But"ter*nut`\, n.
(Bot.) An American tree ( Juglans cinerea) of the Walnut family, and its edible fruit; -- so called from the oil contained in the latter. Sometimes called oil nut and white walnut.
(Bot.) The nut of the Caryocar butyrosum and Caryocar nuciferum, of S. America; -- called also Souari nut.
Wikipedia
Juglans cinerea, commonly known as butternut or white walnut, is a species of walnut native to the eastern United States and southeast Canada.