Westron, also known as the common speech, was the closest thing to a linga franca on Tolkien’s Middle Earth. As such, it was always translated into English in the texts. In later writings, Tolkien hinted that there was at least a skeleton of an actual Westron language, and that certain person and place names were translated in a way to preserve their meaning in the English translation. For example, the character of Mariadock Brandybuck was Kalimac Brandagamba in the original Westron. Since the shortened version of the name, Kali, means Jolly or Merry, the translated name shortens to Merry in order to keep the meanings similar.
The language Rohirric is translated into Old English in the Lord of the Rings novels, since it was an archaic cousin to Westron, which both descended from the Adûnaic language. The language does include some Scandinavian names, such as Westfold.
In his journals, Tolkien wrote extensively on Adûnaic, the ancient ancestor of Westron and Rohirric. One fascinating aspect of the language is that there were four word genders, male, female, neuter and common. Common referred to groups that could include both men and women. Unlike languages like German or Swedish, where genders are applied arbitrarily, gender in Adûnaic actually correspond to the noun they are describing.
Some words in Adûnaic are:
mîk baby boy