"governor of a Turkish district," 1590s, from Turkish bey, a title of honor, the Osmanli equivalent of Turkish beg.
title among Turkish peoples traditionally given to rulers of small tribal groups, to members of ruling families, and to important officials. Under the Ottoman Empire a bey was the governor of a province, distinguished by his own flag (sancak, liwa). In Tunis after 1705 the title become hereditary for the country's sovereign. Later "bey" became a general title of respect in Turkish and Arab countries, added after a personal name and equivalent to "esquire" (or "sir" in conversation) in English. In the 20th-century Turkish republic, bey, though surviving in polite conversation, was replaced by bay before the name (equivalent to "Mr.").