Actually, the Christmas Tree probably comes from when they used a tree hung with balls to represent the Tree of Knowledge in the Garden of Eden hung with fruit. It was part of a sacred play that was performed around Christmas, much like a modern Lesson & Carols Service. They used an evergreen, of course, because it was December, and it was green.
However (and it's a big however) there is something similar in some pagan traaditions. And as frequently happens with rite and ritual, diferent religions have similar motifs coincidentally, and they wind up borrowing ideas from each other, originating with those similarities. The process is very dynamic, and not at all linear and direct.