The Vaathkree trade tongue, a little-known and potentially dead language, represented one of the six million languages C-3PO was fluent in. He proposed employing it as a cipher when speaking to Wedge Antilles during the Battle of Filve, but Han Solo reminded him that Wedge didn't understand the Vaathkree trade language.
As the FarStar approached Demonsgate, it received an SOS transmitted in the Vaathkree trade tongue.