One of the most recognizable titles of Jesus in the Advent season is "Emmanuel." This title is in the final antiphon of the Great Antiphons.
O Emmanuel, our King and Giver of Law:
come to save us, Lord our God!
The prophet Isaiah refers to this name directly and is the most explicit reference to Jesus.
Therefore the Lord himself will give you a sign. Behold, a young woman shall conceive and bear a son, and shall call his name Immanuel.
This Hebrew name means literally, "God is with us" and most fully realized in the person of Jesus Christ.
Jesus' presence continues with us in the Eucharist in a unique, which is why this title is often seen as a eucharistic foreshadowing.
Christmas celebrates the profound truth of God being "with us" in the presence of Jesus Christ.