"GOP" is a nickname for the Republican Party of the United States and stands for "Grand Old Party." The acronym reportedly dates all the way back to 1875, though the meaning has changed since its initial conception.
The initial meaning of "GOP" in 1875, according to the Republican National Committee, was "Gallant Old Party." During the early 20th century and the early years of the automobile, "GOP" was also briefly used to mean "Get Out and Push." Aside from the nickname GOP, the Republican Party also uses a symbol of an elephant, which first was used in an 1874 cartoon.