Mithrasmas

Etymology
. In reference to one Roman Dies Natalis  associated with December 25 and unrelated to Mithraism. Sol Invictus was also conflated with or used as an epithet of Mithras, from where the confused misidentification arose. Apparently coined by.

Proper noun

 * 1)  Christian or secular holiday held on December 25, presented as linked to Mithras