The line comes from South Park's 2006 episode Make Love, Not Warcraft, a parody of the online game World of Warcraft in which four boys try to defeat a player who has spent years grinding to an unbeatable level. The joke turns gaming slang on its head, since a no-lifer is a player accused of having no life outside the game, so defeating him poses a comic paradox. Clipped and shared online, it became a shorthand insult for obsessive play, and it still circulates because almost every gaming group has someone who fits the joke.