While the authorship of the Regina Caeli is unknown, the hymn has been traced back to the twelfth century. It was in Franciscan use, after Compline, in the first half of the following century. There is a legend that says St. Gregory the Great (d. 604) heard the first three lines chanted by angels on a certain Easter morning in Rome while he walked barefoot in a great religious procession and that the saint thereupon added the fourth line: “Ora pro nobis Deum. Alleluia.”