zechariah 12:11 In that day shall there be a great mourning in Jerusalem, as the mourning of Hadadrimmon in the valley of Megiddon. - Free Bible Online

      11. As in Zec 12:10 the bitterness of their mourning is illustrated by a private case of mourning, so in this verse by a public one, the greatest recorded in Jewish history, that for the violent death in battle with Pharaoh-necho of the good King Josiah, whose reign had been the only gleam of brightness for the period from Hezekiah to the downfall of the state; lamentations were written by Jeremiah for the occasion (2Ki 23:29, 30; 2Ch 35:22-27).
      Hadad-rimmon--a place or city in the great plain of Esdraelon, the battlefield of many a conflict, near Megiddo; called so from the Syrian idol Rimmon. Hadad also was the name of the sun, a chief god of the Syrians [MACROBIUS, Saturnalia, 1.23].

JFB.