Farsi (or Persian) was a Human language spoken by the peoples of Persia. It was also spoken on the colony of New Persia, where Starfleet Ensign Rustam Kavousi learned it while growing up. Several of Kavousi's fellow officers posted on planet Obsidian were also able to pick up enough of this language to understand Kavousi's muttered insults. (TOS novel: Vulcan's Forge)