Jenneria has no common tongue, at least, not as such. There is a “Trade Tongue” that is used by most civilized races, and is pretty universally understood, but it is largely unsuited for expressing ideas more complex than how many cows one bale of hay will feed.
Characters begin speaking a regional tongue appropriate to the region they hail from, a racial tongue (if non-human), and Trade Tongue. Other languages may be available, depending upon the character’s Intelligence score. Most people capable of speaking more than one language also speak the languages of nearby regions.
The regional tongue of Valenor is Valoran, and it is spoken by most natives of the region. The regional tongue for Darquemoor is also Valoran, as Darquemoor was only recently annexed from Valenor. The regional tongue for Thetia is Thetian, a form of ancient Arcadian. The people of Haven, what few remain in that shattered wasteland, speak Glantrian, a language all their own.
Giant is known as Jottun in Jenneria, and the Goblin tongue is called Goblini.