This is from P H Reaney and R M Wilson, A Dictionary of English Surnames: The Standard Guide to English Surnames (Oxford, Oxford University Press, 1996), p 458.Turnbull, Turnbill: Willelmus dictus Turnebule 1314 Black; William Turbolle 1327 (Subsidy Rolls Suffolk); Walter Tornebole c1354 Black; Richard Turnebull 1379 (Yorkshire Poll Tax Return); David Trumble orTurnbull 1495 Bardsley. There can be no doubt that this much-discussed surname is a nickname "turn bull," indicative of strength or bravery. The name appears to be northern, particularly Scottish, but early examples are not common. Black's derivation from Trumbald cannot be correct. The early forms of Trumble are quite distinct from Turnbull and there is no proof that any of the 15th-century Scottish Trumbles wereTurnbulls. The Fife families of Trimbill, Trombill and Trumble may wellhave owed their name, as Black suggests, to the same place from which Robert the Tremblee (1296) came. Old English Trumbeald developed naturally to Trumball, also spelled Trumbull. It is much more likely that this should be corrupted to Turnbull than that Turnbull should become an unintelligible Trumbull, Trumble. The nickname origin of the surname is proved by Even himself (despite his antipathy to nicknames)in his reference to a Yorkshire horse named Turnebull (1358) and is confirmed by the modern French Tournebouf which Dauzat explains as a name for a drover.