The first certain documentary reference to the river is as Irym in the cartulary of Buckfast Abbey, dated 1240. Other early recorded forms are Hyrm, Irm, Erm and, in the mid 16th century, Arme. The derivation of the name remains unknown. Ekwall's suggestion that it is a back-formation from Ermington is now thought to be unlikely. Tristram Risdon, in his 1811 Survey of Devon gives an alternate name for the River Erme as the River Arme. He also refers to the mouth of the River Erme as Armouth.Risdon T (1811), The Chorographical Description or Survey of the County of Devon In Donn's map of Devon published in 1765, the village of Mothecombe at the mouth of the river, is referred to as Muddicomb.Donn, Benjamin; A map of the County of Devon
