From BiblePortal Wikipedia

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [1]

Originally the name of an Arab tribe, then applied to the Bedouin, and later to all the Moorish or Mohammedan people who invaded Europe, and against whom the Crusaders fought. The true derivation of the word was long a puzzle to philologers: Du Cange deduced it from Sarah, the wife of Abraham; Hottinger (Biblioth. Orient.) from the Arab saraca, to steal; Forster (Journey) from sahra, a desert; others from the Hebrew sarak, poor. The opinion most generally prevalent is that the word was originally Sharkeyn (Arab. Eastern people), corrupted by the Greeks into Σαρακηνοί , from which the Romans derived their word Saraceni. (See Crusades); (See Moors); (See Spain).

The Nuttall Encyclopedia [2]

The name given in mediæval times to the Arabs or Mohammedans, and extended to all the non-Christian races with whom the Crusaders or Christian races came to grips.