The valley Gehennon, called also the valley of Tophet. Gehennon is the Syriac word for hell. The same is meant by Tophet. These several names it should seem, were all equally applied to the same place. The prophets Isaiah and Jeremiah both speak of this awful spot. (Isaiah 30:33; Jeremiah 7:31) And it is said, that Josiah, the good king, "defiled the place;" that is, he destroyed it for the purpose for which it had been used, by those wretched parents who had been deluded to sacrifice their children to the idol-god Molech, in this spot. (See 2 Kings 23:10) For by destroying it, that cruel, unnatural, and impious practice could no more be done there. Some have thought, that the name Tophet took its rise from Thoph, a drum; for it is supposed, that this, and perhaps other musical instruments, were loudly sounded upon those occasions, to drown the piercing cries of the poor children. The name of Hinnom is derived from the sons of Hinnom. (Joshua 15:8)
See Molech