In a brief search, I discovered in Wikipedia that Nazareth is also the same word of a plant short and conclude this verse is what Luke is reffering to: Isaiah 11:1, "Then a shoot will spring up from the stump of Jesse..." referring to the heritage of Jesus, not the settlement of Nazareth. You did a better job saying this, and I was relieved that this article went in this direction (I wasn't sure when I read the title.)