Toponymy
The name Cornwall comes from combining two different terms from separate languages. The Roman term for the Celtic tribe which inhabited what is now Cornwall at the time of Roman rule in Britain, Cornovii, came from a Brythonic tribal name which gave modern Cornish Kernow, also known as Corneu to the Brythons. This could be from either of two sources; the common Celtic root cern, or the Latin cornu, both of which mean "horn" or "peninsula", suggestive of the shape of Cornwall's landmass. There is a problem with this theory however. At least two other known Celtic tribes bore the name Cornovii, one tribe in Caithness which may also be considered a "headland" or "horn-land", yet another, the principal tribe known to the Romans as Cornovii lived in the West Midlands and Powys areas, calling into question the derivation of the name from a peninsula (however, Celtic tribes were not necessarily permanently settled, and the Latin forms may be based on different British names). Another theory suggests that the name of the Cornovii tribes may well be connected to totemic worship of the "horned god" such as the Gaulish Cernunnos, or a similar totemic cult. Nevertheless, the Cornovii were sufficiently established in the present day area recognised as Cornwall for their territory to be recorded as Cornubia by 700 AD, and remained as such into the Middle Ages. The Ravenna Cosmography, of around 700, makes reference to Purocoronavis, (almost certainly a corruption of Durocornovium), 'a fort or walled settlement of the Cornovii', (unidentified, but possibly Tintagel or Carn Brea).
During the 6th and 7th centuries, the name Cornubia became corrupted by extensive changes in the Old English language. The Anglo-Saxons provided the suffix wealas, meaning "foreigners", creating the term Corn-wealas, Cornouaille in French – also the name of a corresponding Breton colonial territory–and Cornugallia in medieval Latin. Some historians note that this was the word for Wales, however it is understood that the term applied instead to all Brythonic peoples and lands, who were considered foreign by the Anglo-Saxons. As Cornwall was known as West Wales and present-day Wales as North Wales during those times, the "Wales" meaning is probable.
Read more about this topic: Cornwall