The O-Antiphons have been immortalized in part in the traditional Advent hymn, "O come, O come, Emmanuel." They represent some of the Old Testament's prophesies and "names" for the coming Christ. Here is the entire list of these O-Antiphons in an ancient prayer form, representing the hope and anticipation we have for the Messiah. 

O Wisdom, proceeding from the mouth of the Most High, pervading and permeating all creation, mightily ordering all things: Come and teach us the way of prudence.

O Lord of Might and Ruler of the house of Israel, who appeared to Moses in the burning bush and gave him the Law on Sinai: Come with an outstreched arm and redeem us.

O Root of Jesse, who stand for an Ensign of the peoples, before whom the nations will do homage: Come quickly to deliver us.

O Key of David and Scepter of the house of Israel, you open and no one can close, you close and no one can open: Come and rescue the prisoners who are in darkness and in the shadow of death.

O Dayspring, Splendor of Light everlasting: Come and enlighten those who sit in darkness and in the shadow of death.

O King of the nations, the Ruler they long for, the Cornerstone uniting all people: Come and save us all, whom you formed out of clay.

O Emmanuel, our King and our Lord, the Anointed for the nations and their Savior: Come and save us, O Lord our God.

The O-Antiphons were prayed, one each day, Dec. 17-23, in anticipation of the Eve of Christ's birth.

Interestingly, if you take the first letter of each antiphon (in a different order) from their original Latin:

Emmanuel
Radix (root of Jesse)
Oriens (rising dawn)
Clavis (key of David)
Rex (king of the nations)
Adonai (Lord of might)
Sepientia (wisdom)

= EROCRAS = "I'll be there tomorrow"

We will be there tomorrow to welcome our Savior, the Christ.