Celtic toponymy from Brythonic *"crüg" 'hill' (Irish "cruach") From tribal name "Dumnonii" or "Dumnones", from Celtic *"dumno-" 'deep', 'world' From Celtic *"dubr-" 'water', *"dubrās" 'waters' (Welsh "dwfr"; Breton "dour") First element is possibly "dun", ' hill fort' (Welsh ddin, 'fort'). First element from Celtic *"duro-" 'fort'; in "Dūrobrīvae", Celtic *"brīwa" 'bridge' Possibly derived from Brythonic *"iska", 'water, fish' and *"leith", 'damp, wet'. From Celtic *"iska" 'water' (Irish "uisce"); second element in "Isca Dumnoniorum" (Exeter) is a tribal name (see "Devon") From Brythonic *"lēd-" [from Celtic *"leito-"] + *"rïd-" [from Celtic *"(φ)ritu-"] = "Grey Ford" From Celtic *"lindo-" 'pool' + Latin "colonia" 'colony'
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