Muon-catalysed fusion is obtained at low temperatures, although as of 2018 its energy yield is less than the muon production requirements. The term "cold fusion" was first used in the 1950s, to refer to μCF. The 1989 Fleischmann-Pons claim of empirical low-temperature fusion, in heavy water electrolysis with a palladium electrode, was soon debunked. Why did this hypothetical example of fusion take the existing name, "cold fusion"?