The village name means the "thorn-tree settlement on the moor" derived from the Old English, "þorn" meaning a hawthorn tree, "tūn", a farmstead and "mōr", marsh or barren upland. Recorded as Torentun in the 11th century and Thornton in Mora or Thornton super Moram from the 13th to the 15th centuries, the village was probably held before the Norman Conquest of England by Edmund but by 1086 was recorded in the "Domesday Book" as belonging to Robert Malet. The manor consisted of five carucates. It was divided into three fees. In the late-13th century two carucates belonged to the barony of Greystock. Another part consisting of 2½ carucates was part of the Honour of Eye held of the Earl of Cornwall in the late-13th century who before 1312 granted nine oxgangs of land to Fountains Abbey. The third holding belonged to Thomas de Otterington in 1300.