GG comes from online multiplayer gaming, where players type good game at the end of a match as a sign of sportsmanship. Adding ez, short for easy, flips that courtesy into a taunt, and freakin is added for extra emphasis without swearing. The phrase spread through shooters, MOBAs and voice chat lobbies in the 2010s, then into edits, soundboards and short form video as a shorthand for a humiliating, one sided win that needs no explanation.