Both the Ninth Doctor and the Master spoke in Tersuran to bribe the architect of Castle Tersurus to pull the other into a trap, anticipating that the other party would bribe him. Later, when the Master gave the Daleks the secrets of the zectronic beam, the Doctor tried to warn the Master that the Daleks would exterminate him once they were done with him. The Doctor did this in Tersuran, as the Daleks didn't have noses. (TV: The Curse of Fatal Death)