Nothing, indeed, can be more deceptive than the common fashion, of quoting a Roman name from the often blundering lists of the Itineraries, and then passing on at once to the modern English form, without any hint of the intermediate stages. To say that Glevum is now Gloucester is to tell only half the truth; until we know that the two were linked together by the gradual steps of Glevum castrum, Gleawan ceaster, Gleawe cester, Gloucester, and Gloster, we have not really explained the words at all. By beginning with the least corrupt forms we shall best be able to see the slow nature of the change, and we shall also find at the same time that a good deal of incidental light is shed upon the importance and extent of the English settlement.
Doncaster is an excellent example of the simplest form of modernisation. It appears in the Antonine Itinerary and in the _Notitia Imperii_ as Danum. This, with the ordinary termination affixed, becomes at once Dona ceaster or Doncaster. The name is of course originally derived in either form from the river Don, which flows beside it; and the Northumbrian invaders must have learnt the names of both river and station from their Brigantian British serfs. It shows the fluctuating nature of the early local nomenclature, however, when we find that Bæda ('the Venerable Bede') describes the place in his Latinised vocabulary as Campodonum--that is to say, the Field of Don, or, more idiomatically, Donfield, a name exactly analogous to those of Chesterfield Macclesfield, Mansfield, Sheffield, and Huddersfield in the neighbouring region. The comparison of Doncaster and Chesterfield is thus most interesting: for here we have two Roman Stations, each of which must once have had two alternative names; but in the one case the old Roman name has ultimately prevailed, and in the other case the modern English one.
The second best example of a Caster, perhaps, is Lancaster. In all probability this is the station which appears in the _Notitia Imperii_ as Longovico, an oblique case which it might be hazardous to put in the nominative, seeing that it seems rather to mean the town on the Lune or Loan than the Long Village. Here, as in many other cases, the formative element, vicus, is exchanged for Ceaster, and we get something like Lon-ceaster or finally Lancaster. Other remarkable Casters are Brancaster in Norfolk, once Branadunum (where the British termination _dun_ has been similarly dropped); Ancaster in Lincolnshire, whose Roman name is not certainly known; and Caistor, near Norwich, once Venta Icenorum, a case which may best be considered under the head of Winchester. On the other hand, Tadcaster gives us an instance where the Roman prefix has apparently been entirely altered, for it appears in the Antonine Itinerary (according to the best identification) as Calcaria, so that we might reasonably expect it to be modernised as Calcaster. Even here, however, we might well suspect an earlier alternative title, of which we shall get plenty when we come to examine the Chesters; and in fact, in Bæda, it still bears its old name in a slightly disguised form as Kaelca ceaster.