This is an English locational surname, which could be said to have Roman origins. It is locational from one of the varied places called Casterton in the counties of Westmorland, Rutland and Lincolnshire. The derivation is from the original Latin word "castra" meaning a fort, and the later pre 7th century Olde English word "tun" describing a village or settlement. The first known recording of any of the place names is in the famous Domesday Book, when Castretune in Westmorland is so recorded, appearing as Castreton two centuries later in 1222. Surprisingly this particular village does not seem to have produced any nameholders, as the surname does not appear at all in the surving church records of that county. This is not so in both Rutland, Englands smallest county, and Lincolnshire where the surname is well recorded from Stuart times. It would seem that in Lincolnshire the village was "diminished" to the point where it became known only for the manor house of Casterton. This was often the case in the 17th century when the onset of the Industrial Revolution also caused great changes in the countryside. Sheep farming for the fleece, required far fewer workers, taking precedence over former arable lands. As a result villagers left the land, and took or were given, as their surname, the name of their former home. In this case early examples of the surname recording include Robertus Casterton who married Sarah Turner at Empingham, Rutland, on August 29th 1669, and Bridget Casterton who married Thomas Burton at Bourne in Lincolnshire, on Septemer 14th 1682.