Westron, also known as the Common Speech, is the most widespread language spoken by the Free Peoples. It is the native language of many Men and Hobbits, and is understood by those who have dealings with them.
Westron originates from Adûnaic, the language of Númenor. During the height of their power, the Númenóreans had many forts and havens along the western coast of Middle-earth. The Adûnaic spoken there became blended with the languages of the natives into a Common Speech. After the Downfall of Númenor, the founders of Arnor and Gondor used Westron in the governing of their realms and dealings with other folk. They expanded the language with words of Elvish origin.
Some Archaic Westron terms, especially place names, persist to the current time although the words have since changed form or fallen out of common usage. Examples include Michel "Great", as in Michel Delving, and Isenmouthe "Iron Mouth".
All instances of real-life languages in the books and the game are supposed to be translations; none of the characters are actually meant to be speaking English or any other known real-life language. J.R.R. Tolkien translated Westron into English for the sake of putting the readers in the perspective of the Hobbits, rather than having every language be alien to modern ears. Translations of the books and games would thus use the language of the translation to represent Westron.
Older words and forms of English are used to represent Archaic Westron words, however this should not be confused with the use of Old English to represent Rohirric.