From Online Dictionary of Crystallography

Lepton (Fr). Lepton (Ge). Leptone (It). レプトン (Ja). Лептон (Ru). Leptón (Sp).

Lepton is a term introduced by Friedrich Rinne (1924) to indicate electrons, atoms, ions, radicals, and molecules building the unit formula of a crystalline compound. The crystal structure of a solid was sometimes called 'leptonic structure'.

Today, the term lepton is used to indicate spin-1/2 particles and Rinne's use is only of historical interest.