The line comes from Star Trek: The Original Series, which first aired in 1966, where DeForest Kelley played Dr. Leonard McCoy, the Enterprise's chief medical officer. McCoy repeatedly pronounced crew members and aliens dead in his blunt bedside manner, and the phrase hardened into one of the show's most quoted catchphrases alongside lines from Kirk and Spock. Decades of reruns, parodies and fan references kept it alive, and short audio clips later turned it into a staple reaction sound for videos and streams about failure, defeat and anticlimax.