GMC stands for General Motors Company, which was formed in 1909 when General Motors acquired the Rapid Motor Vehicle Company. GMC was originally known as the General Motors Truck Company, keeping this name until 1996 when GMC decided to drop the word “Truck.”
William Durant was the founder of General Motors but was kicked out of the company in 1910 for failing to repay loans. He went on to found Chevrolet, bringing the brand to General Motors when he bought back into the company in 1917. Chevrolet is still owned by GM, and although Chevrolet and GMC trucks are separate brands, they are manufactured in the same plants and include the same parts, barring the trim.