This is a proper Advent hymn and we sang this at church on the first Sunday of Advent. I have to say it seemed odd to be singing about Israel with all the horrors going on there, does anyone on either side care?
This version just says it's by a traditional choir.
Oh Come, Oh Come, Emmanuel was probably written in the early C18. But it's origins are much earlier. From a series of verses or prayers called antiphons known as ' the seven 'O's' from way back in the Middle Ages. These were sung in medieval monasteries.
The words were translated from the Latin by John Mason Neale, one of the best known translators between 1818 -66. The tune is much older possibly from a plainsong chant.