irmologion
A liturgical book containing irmoi for the various canons chanted during the morning service.
Although an Irmologion, as its name suggests, is essentially a collection of irmosy or the nine hymns sung during Matins, the earlier Belorussian Irmologia contain in addition all manner of chants from the Holy Liturgy, Vespers and Matins, Festival and Holy Week services, […]
Where it comes from
From Ancient Greek εἱρμολόγιον (heirmológion).
Adapted from the Wiktionary entry irmologion (CC BY-SA 4.0).