Boyd’s Bible Dictionary:
(wailing). A narrow valley south and west of Jerusalem (Josh. 15:8; 18:16), where Molech was worshipped (1 Kings 11:7; 2 Kings 16:3); hence called Tophet, “drum,” noise (Isa. 30:33); defiled (2 Kings 23:10), and called ge-Hinnom, gehenna, “place of Hinnom,” to type a place of eternal torment. “Hell” in N. T. (Matt. 5:22,29; 10:28; 23:15; Mark 9:43; Luke 12:5).
Concise Bible Dictionary:
This is often called “the valley of the son of Hinnom,” but who Hinnom and his son were is unknown (Josh. 15:8; Josh. 18:16; Neh. 11:30). The valley running from east to west, on the south of Jerusalem, now bears the above name. In some part of this, supposed to be the east end, children were passed through the fire to false gods (Jer. 7:31-32; Jer. 32:35). To prevent this Josiah defiled TOPHETH in this valley (2 Kings 23:10; 2 Chron. 28:3; 2 Chron. 33:6). The prophet Isaiah gives the key to its being associated in the New Testament (under the name of GEHENNA) with eternal punishment: “Tophet is ordained of old; yea, for the king it is prepared; he hath made it deep and large: the pile thereof is fire and much wood; the breath of the Lord, like a stream of brimstone, doth kindle it” (Isa. 30:33). See HELL. In God’s judgments the valley shall become the “valley of slaughter” (Jer. 19:2-14).