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.
Northern English (chiefly Northumbrian) and Scottish: variant, altered by folk etymology, of Trumble, on theory that it denoted a nickname for a man thought to be strong and brave enough to turn back a charging bull, from Middle English turn(en) ‘to turn’ + bul(l)e ‘bull’.