J.R.R. Tolkien called the language of Númenor Adûnaic.
Adûnaic, also spelled Adunaic, is the language associated with the Men of Númenor in Tolkien’s legendarium. Tolkien developed material for it especially in connection with The Notion Club Papers and related writings, and elements of the language appear in names and terms connected with Númenórean history.
Adûnaic is distinct from Quenya and Sindarin, the major Elvish languages most familiar from The Lord of the Rings. It is also different from Khuzdul, the secret language of the Dwarves. Tolkien’s linguistic world contains many languages with different histories, speakers, and relationships, so identifying the people of Númenor is essential to answering this question.
The spelling uses a circumflex over the u: Adûnaic. The language’s name is connected with the Númenórean word adûn, meaning “West” in Tolkien’s linguistic material. Tolkien left much of Adûnaic less fully developed than his best-known Elvish languages, but its place in the history of Númenor is clearly established.