The name of a county often gives a clue to how it was formed, either as a division that took its name from a centre of administration, an ancient kingdom, or an area occupied by an ethnic group. The majority of English counties are in the first category, with the name formed by combining the central town with the suffix "-shire", for example Yorkshire. Former kingdoms, which became earldoms in the united England did not feature this formulation; so for Kent, the former kingdom of the Jutes, "Kentshire" was not used. Counties ending in the suffix "-sex", the former Saxon kingdoms, are also in this category. Many of these names are formed from compass directions. The third category includes counties such as Cornwall and Devon where the name corresponds to the tribes who inhabited the area. County Durham is anomalous in terms of naming and origin, not falling into any of the three categories. Instead, it was a diocese that was turned into the County Palatine of Durham, ruled by the Bishop of Durham. The expected form would otherwise be "Durhamshire", but it was rarely used.
There are customary abbreviations for many of the counties. In most cases, these consist of simple truncation, usually with an "s" at the end signifying "shire", such as "Berks" for Berkshire or "Bucks" for Buckinghamshire. Some abbreviations are not obvious, such as "Salop" for Shropshire, from the Norman-derived word for its county town Shrewsbury; "Oxon" for Oxfordshire, from Latin Oxonium (referring to both the county and the city of Oxford); "Hants" for Hampshire; and "Northants" for Northamptonshire. Counties were often prefixed with "County of" in official contexts, such as "County of Kent". Those counties named after central towns lost the -"shire" suffix, for example Yorkshire would be known as "County of York". This usage was sometimes followed even where there was no town by that name, such as the "County of Berks". The "-shire" suffix was also appended for some counties, such as "Devonshire", "Dorsetshire" and "Somersetshire", despite their origin. There is still a Duke of Devonshire.