lepton (n.)youdaoicibaDictYouDict[lepton 词源字典]
elementary particle of small mass, 1948, from Greek leptos "small, slight, slender, delicate" (from lepein "to peel," from PIE *lep-; see leper) + -on. Also the name of a small coin in ancient Greece, from neuter of leptos[lepton etymology, lepton origin, 英语词源]