“O Flower of Jesse’s stem, you have been raised up as a sign for all peoples; kings stand silent in your presence; the nations bow down in worship before you. Come, let nothing keep you from coming to our aid.” (O Antiphon for Dec. 19th)
The idea of the "root of Jesse" in Scripture is an interesting one, with a meaning that seems a bit fluid. The natural meaning of "root" is, unsurprisingly, a source or foundation. But as imagery, it also beckons to new growth coming forth from a devastated stump – as if that which grows from the root can be called the root, in the same way that people carry the names of their ancestors. It’s also associated with first fruits offerings.
Jesus complicates this meaning in Mt 22:45 (and parallels) when he says: “If David calls Him ‘Lord,’ how then can the Messiah be his Son?” (HCSB). “Root” takes on characters both etiological and eschatological.
Another “root of Jesse” we find in Scripture is Ruth: a woman of truly great character, as we see in her devotion to Naomi, to Naomi’s people, and to Naomi’s God. It strikes me how much of that same fierce loyalty seems to have made it into the blood of David, when he repeatedly demonstrates in his devotion to Saul, to Jonathan, and to the Lord. There’s a lot of Ruth in David, and I have little doubt that the contemporaries of the young Jesus said something similar of Him: "there’s a lot Mary in that boy." The apple never falls far from the tree, indeed.