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'
Celtic language decline in England England begin to be attested from around 670, pre-eminently in Anglo-Saxon charters; they have been intensively surveyed by the English and Scottish Place-Name Societies. Except in Cornwall, the vast majority of place-names in England are easily etymologised as Old English (or Old Norse, due to later Viking influence), demonstrating the dominance of English across post-Roman England. This has traditionally been seen as evidence for a cataclysmic cultural and demographic shift at the end of the Roman period, in which not only the Brittonic and Latin languages, but also Brittonic and Latin place-names, and even Brittonic- and Latin-speakers, were swept away.