The term GT or Gran Turismo (Grand Touring) was first used as a model name by Lancia when the B20 GT was launched in 1948. This car was one of the most influential post war cars, with the worlds first production V6 engine. In 1962 Ferrari introduced the famous GTO or Gran Turismo Omologato (Homolgation), 39 were built and its now one of the most valuable cars in the world. Of course Pontiac immediately ripped it off and there have been numerous GTs and GT variations since.
Yours truly,
The trainspotter