David already posted what we call them here in SOuth Africa, but they are also called "Iggies" which I guess is more of a nickname for them....
The term "GT" is being used more and more down here these days, however most of the Trevally species along our coast are still referred to as "Kingfish" eg: Bluefin Kingish, Yellowfin Kingfish, Brassy Kingfish, Bludger Kingfish etc...