April 25 is honored in the Liturgy by what is sometimes called Saint Mark’s Procession. The term, however, is not a correct one, inasmuch as the Procession was a privilege peculiar to April 25 previously to the institution of the Evangelist’s Feast, which even as late as the 6th century had no fixed day in the Roman Church. The real name of this Procession is The Greater Litanies. The word Litany means supplication, and is applied to the religious rite of singing certain chants whilst proceeding from place to place in order to propitiate Heaven.  The two Greek words Kyrie eleison (Lord, have mercy on us) were also called Litany, as likewise were the invocations which were afterwards added to that cry for mercy, and which now form a liturgical prayer used by the Church on certain solemn occasions. MORE