Oriens in Latin is the Morning Star, the Dayspring. It calls to mind this verse from Malachi:

But for you who fear my name, the sun of righteousness shall rise with healing in its wings. (Mal. 4:2 ESV)

It is significant that this antiphon is sung on the winter solstice, what Donne called “the year’s midnight.” Day now begins with the sign of the morning star, the spring of the day, the Oriens. So Christ has brought light and life at just the darkest moment. And so He will do for you if you but call on Him.

O Dayspring,
splendor of light eternal and sun of righteousness:
Come and enlighten those who dwell in darkness and the shadow o death.