Sheik \Sheik\, n. [Ar. sheikh, shaykh, a venerable old man, a chief, fr. sh[=a]kha to grow or be old.]

The head of an Arab family, or of a clan or a tribe; also, the chief magistrate of an Arab village. The name is also applied to Mohammedan ecclesiastics of a high grade. [Written also scheik, shaik, sheikh.]

Source: Webster's Revised Unabridged Dictionary (1913)