The Romans record the name of the native British tribe that lived in Dorset as the Durotriges, who were also the tribe of much of Somerset and possibly the New Forest. Sometimes translated as "water dwellers", this name could mean that they were seafarers, but is more likely a reference to the marshy valley of the River Frome which they would have farmed. However, this etymology is unsound, based on the Welsh word "dwr" meaning water; however the earlier form of the word was "dwfr", which suggests an Ancient British ancestor-word *dubro-, not *duro- (this form of the word is preserved in the place-name Dover). Another alternative is "fort-dwellers"; it is known that the Durotriges were still occupying their hillforts at the time of the Roman invasion in 43 AD, whereas in most other parts of Britain they had been abandoned around 100 BC. There is also a Cornish word "dur" meaning "land" or "earth"; hence the Durotriges might also be "land-dwellers", referring to their already important farming tradition: it is known that they were exporting grain to the Roman Empire in large quantities already by the first century BC. The etymology of the first element is thus far from certain, although the second element definitely means "dwellers" (Cornish "tre", "town", "tregez" "have lived"; Welsh "tref" "town").