Finally, we reach O Emmanuel (God-with-us, finally pointing straight at the nativity). If you take the first letters of all the O antiphons, you get OOOOOOO, which isn’t helpful, but if you take the first letters of the words after the O, you get sarcore, which is ero cras backwards; ‘ero cras’ is Latin for ‘I will be there tomorrow’.
O Emmanuel, Rex et legifer noster, exspectatio Gentium, et Salvator earum: veni ad salvandum nos, Domine, Deus noster.
O Emmanuel, our king and our lawgiver, the hope of the nations and their Saviour: Come and save us, O Lord our God.
Here are the links for the complete set from Charpentier’s settings.