The Elvish language Tolkien developed as the prestigious tongue of the Eldar is Quenya.
Quenya is one of Tolkien’s most fully developed invented languages. Within the mythology, it originated among the Elves of Valinor and was associated with the High Elves, or Eldar. Tolkien modeled aspects of its sound and structure on languages including Finnish, while creating its vocabulary and grammar as part of his own linguistic art.
Quenya remained an important ceremonial and literary language in Middle-earth, especially among Elves connected with the ancient western realms. Names such as Eärendil, Galadriel, and Númenor reflect Tolkien’s constructed-language work, although names can have complex histories across different stages of his writing.
Sindarin is another major Elvish language and became more widely spoken in much of Middle-earth. Khuzdul is the secret language of the Dwarves, and the Black Speech was created for the servants of Sauron. These are related to Tolkien’s world-building but are not alternate names for Quenya.