From a trade name, presumably a shortened form of the chemical name.
elon (uncountable)
- (photography) Synonym of metol (“p-methylaminophenol sulfate”)
- lone, Noël, Leno, Noel, leno, neol., Léon, enol, one L, Nole, noël, Leon, nole, noel, NOEL, Elno, León
