The O Antiphons are special because each one emphasizes a different prophetic title of the soon-to-be-born King of Kings as foreshadowed in the Old Testament by the prophet Isaiah: Wisdom, Lord of Israel, Root of Jesse, Key of David, Radiant Dawn, King of All Nations, and Emmanuel.

Additionally, the ancient monks who first assembled the O Antiphons were very creative with the order in which they are prayed.  If one takes the first letter of each antiphon (in the Latin) starting from the last to the first, the word ERO CRAS is formed which translates, "Tomorrow I will come."