Westron was the language of the Dunedain of Middle Earth in the Lord of the Rings series of books by J. R. R. Tolkein. He wrote the books as if they had been translated from Westron (the Common Speech). Westron was the closest to the universal language of Middle-earth. Westron is a western word—not a word from the original language.
Westron as a created language is a derivative of the Aduniac tongue of Numenor, originating as a Creole language on the western coast of Middle-earth where the Numenoreans established forts and outposts for trading. From the west it spread east, with the exception of Mordor.
The translation has many effects on the language and by extension the novels. The ending of the "true" hobbit name was Bilba with an -a. However, the -a ending is associated with a female, so Tolkein changed it to the more masculine -o. Bag End was actually Labin-nec after Labingi, the true form of Baggins.