Gehenna is the English spelling of a Greek word that comes from Aramaic. The word originally meant “the Valley of [the son(s) of] Hinnom” in Hebrew. This was a deep valley that marked the border between the lands of two ancient Israelite tribes: Benjamin and Judah (Joshua 15:8; 18:16). Today, people think this valley is the same as Wadi el-Rababi, a deep valley that runs south of the Old City of Jerusalem, starting near its western wall.
Gehenna in the Old Testament
The place became known for worshiping other gods when some of Judah’s kings ruled there. Kings Ahaz and King Manasseh allowed people to worship false gods like Molech and even kill babies (2 Kings 16:3; 21:6; 2 Chronicles 28:3; 33:6; Jeremiah 19:6; 32:35).
King Josiah ended these evil acts (2 Kings 23:10). The prophet Jeremiah talked about this valley when he warned people about God’s judgment (Jeremiah 2:23; 7:30–32; 19:5–6).
Later, the valley was used to burn trash from the city and the dead bodies of criminals. Some people think Judas, who betrayed Jesus, killed himself near this valley. They also identify the Potter’s Field on the south side of this valley.
Because of all the evil things that happened there, people began to use the name "Gehenna" to mean a place where bad people are punished after they die (1 Enoch 18:11–16; 27:1–3; 54:1; 56:3–4; 90:26; 2 Esdras 7:36; compare Isaiah 30:33; 66:24; Daniel 7:10).
Gehenna in the New Testament
Jesus used this word to talk about where people who do not follow God will go when they die (Matthew 5:22; 10:28; 18:9). Since Gehenna is a place of fire (Mark 9:43), it is also called the lake of fire (Matthew 13:42, 50; Revelation 20:14–15). This is the place where evil people will be sent (Matthew 23:15, 33). Satan and his devils will also be sent there forever (Matthew 25:41; Revelation 19:20; 20:10).
It is important to understand that Gehenna is different from other words about what happens after death. In the Old Testament, “Sheol” is the place where people go right after they die before the last Day of Judgment. The New Testament name for this place is “Hades.” “Gehenna” is the final place where people will be punished forever (compare Psalms 49:14–15 with Matthew 10:28). The Greek word “Tartarus” is only used once in the Bible (2 Peter 2:4). It refers to a special place where God sent some angels who rebelled against him a very long time ago. These angels were part of the first rebellion against God that happened before human history began.