Litany (Greek, "supplication") originally denoted any form of prayer, but the name was afterwards confined to that used in times of special distress, when the people marched in procession through the streets, exclaiming repeatedly, "Lord, have mercy upon us I Christ, have mercy upon us I" The litany, as its name implies, was of Eastern origin. Towards the end of the 5th century it was adopted in Gaul, and from Gaul the litany passed to Rome at the close of the 6th century in the pontificate of Gregory the Great, who divided the citizens into seven classes, appointing a separate procession and litany for each class. This service is called the "Great Litany of St. Mark," because it was held on St. Mark's Day. In course of time numerous invocations to the Virgin, apostles, martyrs, and saints were introduced. When the litany, was translated into English, during the Reformation, these were gradually eliminated, and the service assumed very much the same form that it has now. In the Church of Rome it is used on the Rogation Days, St. Mark's Day, and various other occasions. Its use on Sundays is peculiar to the Church of England.