The hymnody of Advent is exceedingly rich. Among this richness is the classic “O Come, O Come, Emmanuel.” As you open your Lutheran Service Book to this hymn (357), you will also find the Great “O” Antiphons. These ancient prayers have long been used to count down the days until Christmas. As you can see, each begins by addressing the Lord with a different phrase: “O Wisdom,” “O Key of David,” “O Emmanuel,” and so on.
Originally written in Latin, the Great “O” Antiphons create a reverse acrostic with these names of God that begin each prayer. They spell out ero cras; that is, “Tomorrow I will be” (cras means “tomorrow,” while ero is a first-person singular future form of the verb “to be”) or perhaps, “I will be there tomorrow” or “I come tomorrow.”