What name does J.R.R. Tolkien give the Balrog fought by Gandalf in Moria?

J.R.R. Tolkien gives the Balrog fought by Gandalf in Moria the name Durin’s Bane.

Durin’s Bane is a surviving demon of the ancient race known as the Balrogs. It lived beneath the Misty Mountains and was awakened by the dwarves of Khazad-dûm when they mined too deeply for mithril. The creature killed King Durin VI, and the dwarves abandoned their underground city, which later became known as Moria.

In The Fellowship of the Ring, the Balrog confronts the Fellowship on the Bridge of Khazad-dûm. Gandalf battles it while the others escape, and both opponents fall into the depths. Gandalf later returns as Gandalf the White after completing that struggle.

Gothmog is another Balrog mentioned in Tolkien’s wider mythology, but he is associated with the First Age and the fall of Gondolin. He is not the Balrog of Moria, making the two names an important distinction.