Of Germanic origin. The name referred originally to a member of the tribe of the Franks, who are said to have got the name from a characteristic type of spear that they used. When the Franks migrated into Gaul in the 4th century, the country received its modern name of France (Late Latin Francia) and the tribal term Frank came to mean ‘Frenchman’. The name is now also used as a short form of Francis or Franklin.
Polish, Ukrainian, and Jewish (eastern Ashkenazic): from Polish bugaj, Ukrainian bugay ‘ox’, ‘bull’, hence a nickname for a big and vigorous man. The Polish word bugaj also means ‘bend in a river’; in some instances the surname may therefore be topographical.