“Where their worm does not die”
It is better for you to enter the kingdom of God with one eye than to have two eyes and be thrown into hell, where 'their worm never dies, and the fire is never quenched.' (Mark 9:47–48 BSB)
What it sounds like today
'Hell,' an abstract otherworldly realm.
The cultural key
The word is Gehenna: the Valley of Hinnom, a real ravine south of Jerusalem where kings had burned children to Molech (Jeremiah 7:31). Jeremiah cursed it as the 'Valley of Slaughter,' and by Jesus' day it had become the standing byword for fiery judgment. (The popular claim that it was Jerusalem's burning garbage dump first appears around AD 1200 and has no ancient evidence; a good caution about tidy explanations.) Mark alone appends Isaiah's closing line (Isaiah 66:24), the prophet's final image of corpses outside the city: Gehenna's picture completed from the same scriptural well it was first drawn from.
Recovered meaning
Jesus points at a literal cursed valley his hearers could walk to, a place of Israel's worst betrayals, and makes it the picture of where contempt and evil finally lead.