Dumnonii the origin of the interpretation of Dumnonii as "deep valley dwellers" from his understanding of the Welsh of his time. John Rhys later theorized that the tribal name was derived from the name of a goddess, "Domnu", probably meaning "the goddess of the deep". The proto-Celtic root *dubno- or *dumno- meaning "the deep" or "the earth" (or alternatively meaning "dark" or "gloomy") appears in personal names such as Dumnorix and Dubnovellaunus. Another group with a similar name but with no known links were the Fir Domnann of Connacht. The Roman name of the town of Exeter, "Isca Dumnoniorum" ("Isca of
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