The word walnut derives from Old English wealhhnutu, literally "foreign nut", wealh meaning "foreign". The walnut was so called because it was introduced from Gaul and Italy. The previous Latin name for the walnut was nux Gallica, "Gallic nut". The best-known member of the genus is the Persian Walnut (Juglans regia) are the only species which has a large nut and thin shell. The nuts are rich in oil, and are widely eaten both fresh and in cookery. Walnuts are also an excellent source of omega-3 fatty acids, and have been shown as helpful in lowering cholesterol.

In Armenian cuisine, walnuts are preserved in sugar syrup and eaten whole. In Italy, liqueurs called Nocino and Nocello are flavoured with walnuts. In Georgia, walnuts are ground along with other ingredients to make walnut sauce.