According to Professor Robert Greenberg of the San Francisco Conservatory of Music, the 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.” Therefore, the Lord Jesus, whose coming we have prepared for in Advent and whom we have addressed in these seven Messianic titles, now speaks to us, “Tomorrow, I will come.” So the “O Antiphons” not only bring intensity to our Advent preparation, but bring it to a joyful conclusion.
But do not overlook this one fact, beloved, that with the Lord one day is as a thousand years, and a thousand years as one day. The Lord is not slow to fulfill his promise as some count slowness, but is patient toward you, not wishing that any should perish, but that all should reach repentance. (2 Peter 3:8-9)
Even so, come Lord Jesus.