2 Kings 11:2

But Jehosheba, the daughter of king Joram, sister of Ahaziah, took Joash the son of Ahaziah, and stole him from among the king's sons which were slain; and they hid him, even him and his nurse, in the bedchamber from Athaliah, so that he was not slain.

Jehosheba - or Jehoshabeath (2 Chronicles 22:11).

Daughter of king Joram - not by Athaliah, but by a secondary wife.

Stole him from among the king's sons which were slain - either from among the corpses, he being considered dead, or out of the palace nursery.

Hid him ... in the bed-chamber - for the use of the priests, which was in some part of the temple (2 Kings 11:3), and of which Jehoiada and his wife had the sole charge. What is called however, the bed-chamber in the East is not the kind of apartment that we understand by the name, but a small closet, into which are flung during the day the mattresses and other bedding materials spread on the floors or divans of the sitting-rooms at night. Such a 'chamber of beds,' or a lumber-room, was well suited to be a convenient place for the recovery of his wounds, and a hiding-place for the royal infant and his nurse.