Dumnonii the British population, suggesting an ancient connection of peoples along the western Atlantic seaboard. The Latin name for Exeter is Isca Dumnoniorum ("Water of the Dumnonii"). This oppidum (a Latin term meaning an important town) on the banks of I River Exe certainly existed prior to the foundation of the Roman city in about AD 50. "Isca" is derived from the Brythonic word for flowing water, which was given to the River Exe. This is reflected in the Welsh name for Exeter: "Caerwysg" meaning "fortified settlement on the river Uisc". Isca Dumnoniorum originated with a settlement that developed around the
Celtic language decline in England England begin to be attested from around 670, pre-eminently in Anglo-Saxon charters; they have been intensively surveyed by the English and Scottish Place-Name Societies. Except in Cornwall, the vast majority of place-names in England are easily etymologised as Old English (or Old Norse, due to later Viking influence), demonstrating the dominance of English across post-Roman England. This has traditionally been seen as evidence for a cataclysmic cultural and demographic shift at the end of the Roman period, in which not only the Brittonic and Latin languages, but also Brittonic and Latin place-names, and even Brittonic- and Latin-speakers, were swept away.