An Etymological Dictionary of the German Language/Annotated/Walnuß
Walnuß, feminine, ‘walnut,’ Modern High German only, from the equivalent Dutch walnoot; compare Anglo-Saxon wealhhnutu, English walnut, Old Icelandic walhnot; it signifies ‘French or Italian nut.’ The first component is walh-, a term originally applied by the Teutons to the Kelts (at first to the Volcae), but later to the Romance tribes of France and Italy. See welsch.