The Elvish word that opens the Doors of Durin in J.R.R. Tolkien’s The Lord of the Rings is “Mellon.”
“Mellon” is Sindarin for “friend.” The Doors of Durin stand at the western entrance to Moria, also called Khazad-dûm, and their inscription gives a clue: “Speak, friend, and enter.” Gandalf initially interprets this as an instruction to say a password, but later realizes that the word to speak is simply “friend.”
The doors were made by the Dwarf Narvi during the Second Age. Celebrimbor, the Elven-smith of Eregion, helped create their magical designs. They open without visible hinges when the correct word is spoken.
The scene highlights Tolkien’s interest in language and in misunderstandings between cultures. The Fellowship enters Moria through the western gate, but the passage is soon followed by the attack of the Watcher in the Water.