The scholars disagree about when the words to this carol were first written.  It is sometimes erroneously ascribed to St Ambrose of Milan, which would make it 4^th century; other sources suggest the 6^th, 7^th, or 9^th centuries. The music is Gregorian chant.

The Latin words exist in several forms, and they have been translated into English in several versions. The earliest English translation comes to us from John Mason Neale (1818-1866). English hymnody owes him a debt of gratitude for the many well-known hymns that he brought into English from the early and medieval Latin church. In the Advent and Christmas seasons these include “O Come, O Come Emmanuel,” “Of the Father’s Love Begotten,” and “Good Christian Men, Rejoice.” Others, from Palm Sunday and Easter, include “All Glory, Laud, and Honor,” “Come, Ye Faithful, Raise the Strain,” and “The Day of Resurrection.”

Here is Neale’s translation. It is perhaps a bit difficult for our present generation to sing, with its emphasis on the doom faced by a ruined race, and our dread of the judge of the living and the dead; and rare is the congregation that sings all six stanzas, unaltered. Still, there is a lot of theology to ponder here. I particularly like the way Neale’s fourth stanza reflects on the hymn to Jesus from Philippians 2:5-11.

1. Creator of the stars of night,
Thy people’s everlasting light,
Jesu, Redeemer, save us all,
And hear Thy servants when they call.

2. Thou, grieving that the ancient curse
Should doom to death a universe,
Hast found the medicine, full of grace,
To save and heal a ruined race.

3. Thou cam’st, the Bridegroom of the bride,
As drew the world to evening-tide;
Proceeding from a virgin shrine,
The spotless Victim all divine.

4. At Whose dread Name, majestic now,
All knees must bend, all hearts must bow;
And things celestial Thee shall own,
And things terrestrial, Lord alone.

5. O Thou Whose coming is with dread
To judge and doom the quick and dead,
Preserve us, while we dwell below,
From every insult of the foe.

6. To God the Father, God the Son,
And God the Spirit, Three in One,
Laud, honor, might, and glory be
From age to age eternally.

This version, with four stanzas in modernized language, is sung by Brother Alphonsus Mary: https://youtu.be/6fncNCR21_Q