(Scandinavian) Most probably from an Old Norse personal name from Gautr ‘Goth’ + stafr ‘staff’. It has been borne by several kings of Sweden, beginning with Gustav Vasa (?1496–1560), who was elected king in 1523 after freeing Sweden from Danish rule.
German and Jewish (Ashkenazic): from German Nebel ‘fog’, ‘mist’, Middle High German nēbel. This could be a nickname, or alternatively a habitational name from any of several places so named in Schleswig-Holstein and Bavaria. In some cases it may be a shortened form of the Germanic personal name Nibelunc, Nebelung.