Isca Dumnoniorum but seems to have gone into decline prior to the Roman withdrawal from Britain . The name "Isca Dumnoniorum" is a Latinization of a native Brittonic name describing flowing water, in reference to the River Exe. More exactly, the name seems to have originally meant "full of fish" (cf. Welsh "pysg", "fish"), although it came to be a simple synonym for water (cf. Scottish whiskey). This is also reflected in the modern Welsh name for Exeter: "Caerwysg" meaning "fortified settlement on the river Uisc". The same name was used for the River Usk (modern ) in southern Wales, causing the
Dumnonii site of the former "principia" and by the late 2nd century the "civitas" walls had been completed. They were 3 metres thick and 6 metres high and enclosed exactly the same area as the earlier fortress. However, by the late 4th century the "civitas" was in decline. As well as Isca Dumnoniorum, Ptolemy's 2nd century "Geography" names three other towns: The Ravenna Cosmography includes the last two names (in slightly different forms, as "Tamaris" and "Uxelis"), and adds several more names which may be settlements in the territory. These include: Other Romano-British sites in Dumnonia include: New settlements continued to