walnut

Concise Oxford English Dictionary © 2008 Oxford University Press:
walnut/ˈwɔːlnʌt/

▶noun

• 1 an edible wrinkled nut enclosed by a hard shell, produced inside a green fruit.

• 2 the tree which produces walnuts, with compound leaves and valuable wood. [Juglans regia and related species.]

– origin OE walh-hnutu, from a Gmc compound meaning ‘foreign nut’.