Translation (1903) of Frenchmithriacisme, as used in 1899 by Franz Cumont as shorthand for "mystères de Mithra". Cumont was convinced that Mithraism was "Roman Mazdaism", hence his (and earlier) treatments of Latin Mithras and Avestan Mithra as synonyms, and the continuing de-inflection of the Latin name (vocative) as French Mithra.