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
Isca Dumnoniorum the line between the Isca fortress and Topsham was excavated at the site on Topsham Road in 2010. Initial dating suggests that it was occupied at the same time as the Isca fortress, –75. The settlement () of Isca Dumnoniorum seems to have developed around the Roman fortress. It is one of the four cities () attributed to the Dumnonii by Claudius Ptolemy in his 2nd-century "Geography" and it served as the tribal capital () of the Dumnonii. It was also listed on the late-2nd century Antonine Itinerary, where it forms the southern terminus of route 15 () on the