Khuzdul

The Dwarves' name for their own secret language, of which only a few words were ever discovered by outsiders. With the exception of a few fragments and place-names, Tolkien gives us little insight into the Dwarvish tongue (as the Dwarves kept their tongue secret, it is natural that little of it should have survived in records). Our main sources are in words such as Khazad-dûm (Khazâd being Dwarvish for 'Dwarves') and Khuzdul itself, and in the Dwarvish war-cry, 'Baruk Khazâd! Khazâd ai-mênu!' ('Axes of the Dwarves! The Dwarves are upon you!').²

During the Third Age, the Dwarves seem to have considered Khuzdul in much the same way as the Elves of Middle-earth looked on Quenya, as an ancient and noble tongue of the past. The Dwarves would more commonly speak, even among themselves, in the native tongues of the regions in which they lived, to the extent that they took their names from these languages.

The Dwarves also had secret 'inner' names, presumably derived from the Khuzdul tongue, but they were extremely secretive about these, to the extent that they were not even given on their owners' tombs.