This draws on historian Philip Payton (a renowned Cornish expert), from his book 'Cornwall: A History' (1996;2004). The original term for the greater part of the peninsula that makes up the South West of Britain was Dumnonia (the 'mn' produces something like a 'v' sound, making this the ancestor of the name for the neighboring county, Devon). The people west of the Tamar River (which was later set as the boundary separating Cornwall and Devon) were known in Roman times as the Cornovii, which is a cognate for the Cornish-language term for Cornwall, which is Kernow, Payton states that these people 'were established sufficiently for their territory (Cornwall) to be recorded as Cornubia by cAD 700. The root 'corn' means a horn (probably a reference to the Cornish peninsula), a prefix which has given us both Kernow and Cornwall (the later including the Anglo-Saxon suffix 'wealas', foreigner, the same word as in Wales and Welsh).'

So you see, the Corn of Cornwall is not related to the term used in Britain for grain; instead it is related to the term 'cornucopia' - horn of plenty. The second part of the English name 'wall' is from an Anglo Saxon term that was being applied to the Brythonic-Celtic-speaking people to the west before the time of the Norman invasion of 1066; these people were the Welsh and the Cornish - the foreigners who lived removed from the land of the Angles and the Saxons (what we now call England).