Mithraism

Translation (1903) of French mithriacisme, 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.

Mithraism

1. An astrology-based, middle-platonic mystery religion of the 1st-4th century Roman Empire that claimed to have been founded by Zoroaster, admitted only men, and was especially popular among the Roman military.
   • 1920, Edward Carpenter, Pagan and Christian Creeds, New York: Harcourt, Brace and Co., published 1921, page 41:

     It has left many monuments of itself here in Britain. At Rome the worship was extremely popular, and it may almost be said to have been a matter of chance whether Mithraism should overwhelm Christianity, or whether the younger religion by adopting many of the rites of the older one should establish itself (as it did) in the face of the latter.

   • 1925 July – 1926 May, A[rthur] Conan Doyle, “(please specify the chapter number)”, in The Land of Mist (eBook no. 0601351h.html), Australia: Project Gutenberg Australia, published April 2019:

     "Confirmation is mithraism. So is baptism, only it was blood instead of water. As to the sacrificial meal..." Mason put his fingers in his ears.