The following is the explanation by The Marian Catechists, sent via email 12/15/2016, about the O Antiphons. They are to me the continuous desire of the heart for God to come into all hearts, and an opportunity for us all to join the whole Church in this desire.
Also, the link immediately below should bring you to a printable you may use to display the antiphons in your home each day and use at family prayer. Enjoy. And Merry Christmas.
THE O ANTIPHONS by the Marian Catechists:
As her final phase of preparation for Christmas, the Church recites or chants the O Antiphons during Vespers of the Liturgy of the Hours. The O Antiphons express the Church’s longing for and expectation of the Messiah, and her startled wonderment at the fullness of grace which the Christ-Child is about to bestow on the world.
Benedictine monks arranged these antiphons with a definite purpose. If one starts with the last title and takes the first letter of each one — Emmanuel, Rex, Oriens, Clavis, Radix, Adonai, Sapientia — the Latin words ero cras are formed, meaning, “Tomorrow, I will come.” In these words, the Lord Jesus, for whose coming we prepare in Advent and to whom we address these seven Messianic titles, now speaks to us. The O Antiphons not only bring intensity to our Advent preparations, but they bring our preparations to a joyful conclusion. Dec. 17 – O Sapientia: O Wisdom (Eccl 24: 5), you came forth from the mouth of the Most High (Sir 24: 30) and, reaching from beginning to end, you ordered all things mightily and sweetly (Wis 8: 1). Come, and teach us the way of prudence (Isa 40: 14).
Dec. 18 – O Adonai: O Adonai or O Lord and Ruler (Exod 6: 13) of the house of Israel (Matt 2: 6), you appeared to Moses in the fire of the burning bush (Exod 3: 2); on Mount Sinai, you gave him your Law (Exod 20). Come, and with outstretched arm, redeem us (Jer 32: 21).
Dec. 19 – O Radix Jesse: O Root of Jesse, you stand for the ensign of all mankind (Isa 11: 10); before you, kings shall keep silence and, to you, all nations shall have recourse (Isa 52: 15). Come, and save us, and do not delay (Hab 2: 3).
Dec. 20 – O Clavis David: O Key of David (Apoc 3: 7), Scepter of the House of Israel, you open and no man closes; you close and no man opens (Isa 22: 22). Come, and deliver him from the chains of prison who sits in darkness and in the shadow of death (Ps 107: 10).
Dec. 21 – O Oriens: O Rising Dawn (Zac 6: 12), Radiance of the Light eternal (Hab 3: 4) and Sun of Justice (Mal 3: 20), come, and enlighten those who sit in darkness and the shadow of death (Ps 107: 10; Lk 1: 78).
Dec. 22 – O Rex Gentium: O King of the Gentiles (Hag 2: 8), Desired of all, you are the cornerstone that binds two into one (Eph 2: 20). Come, and save poor man whom you fashion out of clay (Gen 2: 7).
Dec. 23 – O Emmanuel: O Emmanuel (Isa 7: 14; 8: 8), our King and Lawgiver (Gen 49:10; cf. Ezek 21: 32), the Expected of the nations and their Savior (Isa 33: 22), come, and save us, O Lord our God.