Black Chasm

Khazad-dûm was once one of the great wonders of the world, mightiest and oldest of the Dwarf-cities. After the awakening of the Balrog known as Durin's Bane in III 1980, the Dwarves were driven out of their ancient home and it fell into darkness. After that time its name was changed, at least in Elvish, to Moria. That name derives from mor, 'black' or 'dark', and iâ, 'void' or 'abyss', and so the name Moria is variously translated into English as the 'Black Chasm' or the 'Black Pit'.

Durin's Bane was destroyed by Gandalf during the War of the Ring, and according to some legends, Khazad-dûm was refounded many years afterwards by Durin VII, heir to the royal line of the Longbeards. If this is true, then presumably the name 'Black Chasm' would have fallen out of use, and the old and noble Khazad-dûm, 'mansion of the Dwarves', would have come back into common usage.