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
England–Wales border Insular Celtic languages, and were regarded as Britons. The clear geographical divide between the mountainous western areas of southern Britain and the generally lower-lying areas to the east was reflected in the pattern of Roman occupation. The main Roman military bases for the control of what became Wales were beyond the mountains, at "Deva" (Chester), "Viroconium" (Wroxeter, near Shrewsbury), and "Isca Augusta" (Caerleon, near Newport), all located close to the later national border. When the Roman garrison left around 410, the various parts of Britain were left to govern and defend themselves. The western area, later Wales, had become largely