The term Saracen comes from Greek sarakenoi. In the early centuries of the Roman Empire it was used as the name of an Arab tribe in the Sinai, apparently taken from the Arabic word sharqiyyin ("easterners").
Later the Greek-speaking subjects of the Empire applied it to all Arabs. After the rise of Islam, and especially at the time of the Crusades, its usage was extended to all Muslims, particularly those in Sicily and southern Italy. In older Western historical literature, the term "Saracen Empire" was often used to refer to the first Arab Caliphate, ruled by the Umayyad and Abbasid dynasties.
In Christian polemical writing against Islam, the name was made to mean "those empty of Sarah" or "not from Sarah," as Arabs were descended from Hagar.