It's assumed all characters can speak the shared language of the Compact that developed originally as a pidgin between the different geographical regions of the five great houses (popularly called Arxian or Compact Common, but also known as low Grayson, Arvi, and others). The linguistics skill is the ability to speak any languages outside of that, particularly from outside the continent of Arvum. Foreign visitors to Arx are uncommon, but the need for translators who can talk to Eurusi dignitaries and not trigger a war does occasionally come up.
Please don't use real-world languages as flavor substitutes without asking first. Some are already used for that purpose and it could give the impression that your character knows languages they would not.