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Adûnaic was derived from the related Bëorian and Hadorian tongues—collectively called Taliska—and during the Second Age a Bëorian accent still survived in parts of Númenor, most notably in Emerië and around the harbour of Andúnië. Most of the House of Bëor had been killed after the Dagor Bragollach, and therefore the Hadorian accent had become most prevalent. Adûnaic seems not to have been influenced by the language of the Second House of Men, the Haladin tongue, at all: when the Númenóreans returned to Middle-earth in the Second Age, they did not recognise the peoples of Enedwaith and Minhiriath as their distant kin, because these spoke Haladin languages.
Those Men who survived the War of Wrath and sailed to Númenor took their language with them, and in Númenor it became known as Adûnaic. Before the Shadow fell upon the isle, Adûnaic was generally considered to be a language of less prestige than the Elven tongues. Thus most important documents and maps of Númenor, and most of the lords and ladies of the Dúnedain, used Quenya or Sindarin names instead of Adûnaic ones. Even most commoners knew Sindarin to some degree. However, about 2,000 years into the Second Age, the Númenóreans' feelings toward the Elves changed: they began to envy the immortality of the Firstborn. These cold feelings extended to the languages of the Elves, and thus the Kings and their followers, the King's Men, used the Elven tongues less and less. Though the Kings and Queens had all taken their names in Quenya, after some time their supporters used Adûnaic translations of these names to refer to them. Eventually, the twentieth King (Ar-Adûnakhôr) took his name in Adûnaic and forbade anyone to speak the Elven tongues in his presence. However, the supremacy of Adûnaic was most strongly enforced by Ar-Gimilzôr the twenty-third King: he outlawed the use of Elvish anywhere in Númenor, which antagonized the few Faithful Númenóreans still living in the land.
However, his son Inziladûn turned from the rebellion of the Kings before him and took a Quenya name again: Tar-Palantir. Tar-Palantir repealed the ban on the Elven tongues and gave peace to the Faithful. His daughter Míriel would probably have continued his reforms, but her cousin Pharazôn seized power and, in addition, gave her an Adûnaic name (Ar-Zimraphel). Ar-Pharazôn was the last of the Kings of Númenor, for when he felt the end of his life drawing near, he took a great army to Aman in an attempt to gain immortality. As a result of this action, Númenor itself was destroyed.
With the Downfall of Númenor came the end of classical Adûnaic. The study and preservation of the language was neglected by the Exiles of Númenor, because they associated it with the rebellious and repressive Númenórean Kings. However, the Westron tongue or Common Speech, widely spoken in Middle-earth during the Third Age, was largely derived from Adûnaic.