The line comes from South Park, the animated series created by Trey Parker and Matt Stone that first aired in 1997, where Kenny McCormick was famously killed in episode after episode during its early seasons. His friends Stan and Kyle would react with the now-famous shout, turning his repeated deaths into a running joke rather than a tragedy. The phrase spread through reruns, clips and internet memes, and the Portuguese version, Mataram o Kenny, kept the same joke alive for Brazilian audiences. It remains popular because it compresses a whole cartoon death into one instantly understood reaction.