Avathar or Avaþar (Q, pron. N [ˈavaθar], V [ˈaβaθar]) was the dark strip of land at the feet of the southern Pelóri Mountains in Aman. It was the home of Ungoliant before she went to Middle-earth with Melkor.
The name "Avathar" has conflicting translations. In "The Later Quenta Silmarillion" section of Morgoth's Ring, Tolkien translates Avathar as "The Shadows" in "ancient" Quenya. However, in the "Quendi and Eldar" section of The War of the Jewels, Tolkien states that Avathar has no Elvish translation, meaning that it must have been adapted from its Valarin name.
In the Quenya of the Noldor, the name must have become Avasar (pron. [ˈavasar]) because of the loss of þ/th in Noldorin Quenya.