Historically, a sheriff was a legal official with responsibility for a "shire" or county. In modern times, 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 reeve". 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. The term was preserved in England notwithstanding the Norman Conquest. From the Anglo-Saxon kingdoms, the term spread to several other regions, at an early point to Scotland, latterly to Ireland and to the United States.
The Arabic term sharif ("noble"), sometimes rendered sherif, bears no historical or etymological connection.