Irmologion is a name of several software products of Vlad Dorosh related to New Church Slavonic typography:
History and name
The Irmologion digital fonts were designed in order to approximate one of the real New Church Slavonic typefaces used at the beginning of the 20th century. They are named after the Orthodox liturgical book Irmologion which was printed in the Russian Empire (in an edition of 1913) with this typeface.
The Irmologion fonts were, and still are, very popular because they were the first high-quality digital fonts for Orthodox liturgical typography in New Church Slavonic publicly available in Russia (the earlier Izhitsa typeface was designed primarily for stylish advertising and for academic Old Church Slavonic typography). However, they have been made obsolete by a remake, the Heirmos font by the same author.