Most people are familiar with the "O" Antiphons because they are paraphrased in the words of the Advent Hymn "O Come! O Come! Emmanuel." In the tradition of liturgucal churches, the "O" Antiphons are sung or recited at vespers from December 17 through December 23. I will be using them for the text of my next seven Advent Calendar Roman windows.
Each antiphon is a name of Christ, one of his attributes mentioned in Scripture. They are:
December 17: O Sapientia (O Wisdom)
December 18: O Adonai (O Adonai)
December 19: O Radix Jesse (O Root of Jesse)
December 20: O Clavis David (O Key of David)
December 21: O Oriens (O Morning Star)
December 22: O Rex Gentium (O King of the nations)
December 23: O Emmanuel (O Emmanuel)
The exact origin of the "O Antiphons" is not known. Boethius (480–524/5) made a slight reference to them, thereby suggesting their presence at that time. At the Benedictine Saint Benedict Abbey abbey of Fleury (now Saint-Benoît-sur-Loire), these antiphons were recited by the abbot and other abbey leaders in descending rank, and then a gift was given to each member of the community. By the eighth century, they were in use in the liturgical celebrations in Rome.