Easton's 1897 Bible Dictionary:

Josiah
   healed by Jehovah, or Jehovah will support. The son of Amon, and
   his successor on the throne of Judah (2 Kings 22:1; 2 Chr.
   34:1). His history is contained in 2 Kings 22, 23. He stands
   foremost among all the kings of the line of David for unswerving
   loyalty to Jehovah (23:25). He "did that which was right in the
   sight of the Lord, and walked in all the way of David his
   father." He ascended the throne at the early age of eight years,
   and it appears that not till eight years afterwards did he begin
   "to seek after the God of David his father." At that age he
   devoted himself to God. He distinguished himself by beginning a
   war of extermination against the prevailing idolatry, which had
   practically been the state religion for some seventy years (2
   Chr. 34:3; comp. Jer. 25:3, 11, 29).

     In the eighteenth year of his reign he proceeded to repair and
   beautify the temple, which by time and violence had become
   sorely dilapidated (2 Kings 22:3, 5, 6; 23:23; 2 Chr. 34:11).
   While this work was being carried on, Hilkiah, the high priest,
   discovered a roll, which was probably the original copy of the
   law, the entire Pentateuch, written by Moses.

     When this book was read to him, the king was alarmed by the
   things it contained, and sent for Huldah, the "prophetess," for
   her counsel. She spoke to him words of encouragement, telling
   him that he would be gathered to his fathers in peace before the
   threatened days of judgment came. Josiah immediately gathered
   the people together, and engaged them in a renewal of their
   ancient national covenant with God. The Passover was then
   celebrated, as in the days of his great predecessor, Hezekiah,
   with unusual magnificence. Nevertheless, "the Lord turned not
   from the fierceness of his great wrath wherewith his anger was
   kindled against Judah" (2 Kings 22:3-20; 23:21-27; 2 Chr.
   35:1-19). During the progress of this great religious revolution
   Jeremiah helped it on by his earnest exhortations.

     Soon after this, Pharaoh-Necho II. (q.v.), king of Egypt, in
   an expedition against the king of Assyria, with the view of
   gaining possession of Carchemish, sought a passage through the
   territory of Judah for his army. This Josiah refused to permit.
   He had probably entered into some new alliance with the king of
   Assyria, and faithful to his word he sought to oppose the
   progress of Necho.

     The army of Judah went out and encountered that of Egypt at
   Megiddo, on the verge of the plain of Esdraelon. Josiah went
   into the field in disguise, and was fatally wounded by a random
   arrow. His attendants conveyed him toward Jerusalem, but had
   only reached Hadadrimmon, a few miles south of Megiddo, when he
   died (2 Kings 23:28, 30; comp. 2 Chr. 35:20-27), after a reign
   of thirty-one years. He was buried with the greatest honours in
   fulfilment of Huldah's prophecy (2 Kings 22:20; comp. Jer.
   34:5). Jeremiah composed a funeral elegy on this the best of the
   kings of Israel (Lam. 4:20; 2 Chr. 35:25). The outburst of
   national grief on account of his death became proverbial (Zech.
   12:11; comp. Rev. 16:16).


Hitchcock's Bible Names Dictionary (late 1800's):

Josiah, the Lord burns; the fire of the Lord