Early forms of the name Turnbull in Scotland include Turnebule and Tornebole which were both recorded in the fourteenth century. The name is of northern origin and was found on both sides of the Anglo-Scottish frontier in the age of the sixteenth century Border reivers. Enemies of the Turnbulls included the Armstrong clan of the Debatable Land on the border between Cumbria and Scotland. Turnbull is a nickname and literally means 'turns bull'. referring to a person's abilty to become strong or brave when the need arose. In the sixteenth century a Yorkshire horse which displayed these characteristics was known as 'Turnbull'. Another theory for the name is that it is a reference to a drover, which was a common occupation in the Scottish borders. The French word 'Tourneboef' is a word for a drover and may be realted to Turnbull. Some believe that the Fife names Trumble and Trimble, also of Scottish origin are corruptions of Turnbull but a Robert de Tremblee is recorded in the thirteenth century and it may be that these forms derive from this particular name. In Yorkshire a name Trumbald or Thrumball existed as early as 1313 and another form Trumbald occurs in Suffolk in 1327.These names derive from the Anglo-Saxon Trumbeald meaning strong-bold, but again speculation that these names became Turnbull has not been proven. 

Today the name Turnbull is commonest in Northumberland Tyneside, Durham and the Scottish borders.