The word for hell began as a valley outside Jerusalem's walls

The Valley of Hinnom, in Hebrew ge-hinnom, curls around the southwest side of old Jerusalem. Joshua lists it as nothing more than a boundary marker between tribes. What changed its name forever happened under the last kings of Judah: at a site in the valley called Topheth, children were burned as offerings, a practice the kings Ahaz and Manasseh are said to have joined. Jeremiah records God saying of it that such a thing "did not come into my mind," and renames the place the Valley of Slaughter. King Josiah defiled the site so it could never be used again.

The name never recovered. By the Second Temple period, Jewish writers were using ge-hinnom, in Greek "Gehenna," for the destination of the wicked after judgment. So when the Gospels have Jesus warn about being thrown into "Gehenna," the word every English Bible renders "hell," he is naming the ravine within sight of the city walls, with all of that history attached.

One popular detail does not survive checking: the claim that Gehenna was Jerusalem's perpetually burning garbage dump, repeated in a thousand sermons, traces back to a single medieval commentary written around 1200 CE. No ancient text and no archaeology supports it. The fires the Bible actually places in Hinnom were sacrificial ones, which is a darker fact than the legend. Today the valley is a city park, green and quiet, with concert stages in summer.