IRMOS - a word meaning
"link" in Greek. The
Irmos is the theme-song and the first hymn of each ode of a
Canon. It has a double function: it "links" the ode thematically with the Biblical canticle which serves as its prototype, and, by establishing the meter and melody for all the other hymns (
troparia) of the ode, it is the first "link" in their chain.