A sheriff is in principle a legal official with responsibility for a county

County

A county is a jurisdiction of local government in certain modern nations. Historically in mainland Europe, the original French term, comté, and its equivalents in other languages denoted a jurisdiction under the sovereignty of a count A county is a jurisdiction of local government in certain...

. In practice, the specific combination of legal, political, and ceremonial duties of a sheriff varies greatly from country to country.

The word "sheriff" is a contraction of the term "shire

Shire

A shire is a traditional term for a division of land, found in the United Kingdom and in Australia. In parts of Australia, a shire is an administrative unit, but it is not synonymous with "county" there, which is a land registration unit. Individually, or as a suffix in Scotland and in the far...

 reeve

Reeve (England)

Originally in Anglo-Saxon England the reeve was a senior official with local responsibilities under the Crown e.g. as the chief magistrate of a town or district...

". The term, from the Old English scīrgerefa, designated a royal official responsible for keeping the peace (a "reeve") throughout a shire or county on behalf of the king.