Wartaki was the name of an island continent on the planet of Kashyyyk.
It was most likely a large part of the Wartaki Islands. The dialect Xaczik, a difficult dialect, was developed on Wartaki to confuse and/or fool the Wookiees' Imperial slave masters in the Galactic Civil War.
Sources
"Wanted by Cracken" — Star Wars Adventure Journal 10- The Official Star Wars Fact File 42 KAS 1-4: Kashyyyk