Porn loop is a slang term for the pornographic film loops created with Super 8 mm film

Super 8 mm film

Super 8 mm film is a motion picture film format released in 1965 by Eastman Kodak as an improvement of the older "Double" or "Regular" 8 mm home movie format....

starting in the late 1960s through the 1980s. They were largely replaced and phased out by technological improvements to both film-making and distribution including the home movie industry when anyone could purchase a movie to view in private.