DEY, an honorary title formerly bestowed by the Turks on elderly men, and appropriated by the janissaries as the designation of their commanding officers (an adaptation of the Turk. dal, a maternal uncle). In the i7th century the deys of the janissaries in Algeria became the rulers of that country (see ALGERIA: His tory). From the middle of the i6th century to the end of the i7th century the ruler of Tunisia was also called dey, a title fre quently used during the same period by the sovereigns of Tripoli.