In the Ground of the Medium, the central continent of the imaginary world where is held in particular the Seigneur of the Rings of J.R.R. Tolkien, the westron is the common language. The account of the Seigneur of the Rings is supposed to be written in this language of the hand of Bilbon and Frodon Sacquet.

Tolkien does not give practically any element of westron. The existing vocabulary is only of one word hundred, but no structural component was published. Notes exist nevertheless on the evolution of certain words of the Rohanais to the westron.

In certain attempts at Francization of its translators, this language was seen called “Ouistrain” (cf the Lord of the Rings, vol. IV Appendices and Index, éts Christian Bourgois)