Latin survivals
The Latin word castra is an early loan word in Old English as ceaster and appears in place-names as Chester- or -chester. The name is usually applied to a Roman military fortification although in the north it may have been applied to pre-Roman defensive works. The form caster also occurs in the northern counties, and in Lincolnshire, Rutland and Norfolk. The Latin form Castellum seems to be absent although widespread in Gaul where is is usually interpreted to mean "fortified village".

In Britain both forms of castra are applied not only to important military site but also to quite insignificant works and features associated with military works e.g. Chesterfield, Chesterford, Chesterton etc.