This title originally signified the governor of the fourth part of a country. Thus Philip of Macedon divided Thessaly into four districts called ‘tetrarchies.’ Later, however, the title came to be used in a loose sense of any petty ruler, and in this sense it is applied in the NT to Herod Antipas, Philip, and Lysanias. Of these Herod is called ‘king’ in Matthew 14:9; but the usual and correct designation of him is ‘tetrarch,’ and it is thus that he is mentioned in Acts 13:1, the only passage in the apostolic writings where the title occurs.
G. Wauchope Stewart.