"Advent" means simply "arrival" from the Latin for "come" and "to"; Jesus "came to" the world at CHRISTmas - but from where?
We can go back to about 1000 years (BC) for a first clue.
When David was about to die, he called his son Solomon and gave him his last instructions: “My time to die has come. Be confident and determined, and do what the Lord your God orders you to do. Obey all his laws and commands, as written in the Law of Moses, so that wherever you go you may prosper in everything you do. If you obey him, the Lord will keep the promise he made when he told me that my descendants would rule Israel as long as they were careful to obey his commands faithfully with all their heart and soul."
Thus began the embryo of the idea that the "line" of David would continue for ever. Politically, kings did not obey and the Royal line did not continue royally, but it did continue.
A couple of centuries later the prophet Micah reinforced the idea by announcing that God's "man" would, indeed, "come to" Bethlehem.