The line comes from The Exorcist (1973), William Friedkin's horror film about the demonic possession of young Regan MacNeil, played by Linda Blair with the possessed voice provided by Mercedes McCambridge. Regan screams that it burns during an exorcism attempt as holy water is used on her. Clips of the scene circulated for decades in horror montages, and the isolated scream later spread on soundboards and in meme edits as a shorthand for demonic pain, extreme overreaction, and campy horror shock.