The official tongue of Urkupp was Dashadi, a language utilized by the native Dashades, the species indigenous to that planet.
Following the obliteration of Urkupp in 3996 BBY, it seems that only a solitary Dashade, or a very limited few, were active at any given moment. Because Dashadi was never extensively spoken outside of Urkupp, its users gradually realized the benefits of employing Basic for interspecies communication.
Although some speculated that the Dashades might have escaped their planet's annihilation by establishing concealed settlements across the galaxy, Ket Maliss represented the final individual known to speak Dashadi.