The Rice University Neologisms Database

Good game. Initially said after a game as a remark of good sportsmanship. Shortened to gg through initialism. Seems to have undergone perjoration, as when it is said condescendingly from the winner of the game to the loser. Often included in the phrase "gg no re" meaning "good game no rematch." Now often used in situations that do not even involve games, but simply foolish or self-defeating acts.