Geographic clustering of the suffixes:
-caster 
-cester 
-chester 
-cetter/-xeter
-caster 
-cester 
-chester 
-cetter/-xeterThe English place-name Chester, and the suffixes -chester, -caster and -cester (old -ceaster), are commonly indications that the place is the site of a Roman castrum , meaning a military camp or fort (cf. Welsh caer ), but it can also apply to the site of a pre-historic fort. [1] Names ending in -cester are nearly always reduced to -ster when spoken, the exception being "Cirencester", which (commonly nowadays) is pronounced in full. [2] However, names ending in -ster are not necessarily related, as the Irish province of Leinster, which comes from the tribe Laigin + Irish tír or Old Norse staðr, both meaning "land" or "territory". The pronunciation of names ending in -chester or -caster is regular.