Blargian was a language spoken by the Blarg. Ratchet knew how to read Blargian despite being a Lombax.

Ratchet & Clank Going Commando

Even though the Blarg made their first appearance in the original, their language is not noted until Going Commando. While on Joba, Ratchet purchases a Levitator from the Shady salesman. The instructions provided with them were written in Blargian; however, Ratchet knew how to read the Blargian language and installed the Levitator onto Clank.