The seven “O Antiphons” (also called the “Greater Antiphons” or “Major Antiphons”) are prayers that come from the Breviary’s Vespers during the Octave before Christmas Eve, a time which is called the “Golden Nights.”
Each Antiphon begins with “O” and addresses Jesus with a unique title which comes from the prophecies of Isaias and Micheas (Micah), and whose initials, when read backwards, form an acrostic for the Latin “Ero Cras” which means “Tomorrow I come.”
O Sapientia, quae ex ore Altissimi prodiisti,
attingens a fine usque ad finem,
fortiter suaviterque disponens omnia:
veni ad docendum nos viam prudentiae.O Adonai, et Dux domus Israel,
qui Moysi in igne flammae rubi apparuisti,
et ei in Sina legem dedisti:
veni ad redimendum nos in brachio extento.O Radix Jesse, qui stas in signum populorum,
super quem continebunt reges os suum,
quem Gentes deprecabuntur:
veni ad liberandum nos, jam noli tardare.O Clavis David,et sceptrum domus Israel;
qui aperis, et nemo claudit; claudis, et nemo aperit:
veni, et educ vinctum de domo carceris,
sedentem in tenebris, et umbra mortis.O Oriens splendor lucis aeternae,
et sol justitiae: veni, et illumina
sedentes in tenebris, et umbra mortis.O Rex Gentium, et desideratus earum,
lapisque angularis, qui facis utraque unum:
veni, et salva hominem, quem de limo formasti.O Emmanuel, Rex et legifer noster,
exspectatio Gentium, et Salvator earum:
veni ad salvandum nos, Domine, Deus noster.
The 'O' Antiphons - from the Ghent tryptich
These moving “O Antiphons” were apparently composed in the seventh or eighth century when monks put together texts from the Old Testament, particularly from the prophet Isaiah, which looked forward to the coming of our salvation. They form a rich, interlocking mosaic of scriptural images. The great “O Antiphons” became very popular in the Middle Ages when it became traditional to ring the great bells of the church each evening as they were being sung.
December 17th:
O Sapientia (Is. 11:2-3; 28:29): “O Wisdom, you come forth from the mouth of the Most High. You fill the universe and hold all things together in a strong yet gentle manner. O come to teach us the way of truth.”
December 18th:
O Adonai (Is. 11:4-5; 33:22): “O Adonai and leader of Israel, you appeared to Moses in a burning bush and you gave him the Law on Sinai. O come and save us with your mighty power.”
December 19th:
O Radix Jesse(Is. 11:1, 10): “O stock of Jesse, you stand as a signal for the nations; kings fall silent before you whom the peoples acclaim. O come to deliver us, and do not delay.”
December 20th:
O Clavis David (Is. 9:6; 22:22): “O key of David and scepter of Israel, what you open no one else can close again; what you close no one can open. O come to lead the captive from prison; free those who sit in darkness and in the shadow of death.”
December 21st:
O Oriens (Is. 9:1): “O Rising Sun, you are the splendor of eternal light and the sun of justice. O come and enlighten those who sit in darkness and in the shadow of death.”
December 22nd:
O Rex Gentium (Is. 2:4; 9:5): “O King whom all the peoples desire, you are the cornerstone which makes all one. O come and save man whom you made from clay.”
December 23rd:
O Emmanuel (Is. 7:14) : “O Emmanuel, you are our king and judge, the One whom the peoples await and their Savior. O come and save us, Lord, our God.”
Listen to them individually:
O Sapientia
O Adonai
O radix iesse
O clavis David
O oriens splendor
O Rex gentium
O Emmanuel
Catholicism Pure & Simple 
I really like the pic of the choir in the Ghent tryptich singing their litle hearts out!
A cut above the normal Catho art.
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Could this explain the strange title given in Spain to their unique statuary portraits of the Virgin Mary, very pregnant: “The Virgin of the O?” I have wondered, and never managed to get an answer.
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Rebrites: The honest answer – I really don’t know, I have never heard of this title before, but it makes sense as the Mother of the Incarnation to whom these titles are given. I will endeavour to find an answer though as it is an interesting question. Thank you.
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