True names are a rather old concept, originating in religion, I think. They are not just from fantasy stories or anything, they hold a basis in reality. If you wanted to, there are loads of books on the subject, or with the subject in them, that are not fantasy books. (Just in case it sounds like it, I'm not bashing fantasy books or anything, I read them almost exclusively. ^^)
I don't think we should name the tree. Not anything suggested anyway. Glaistig was right about Sage, even though it's overused, I would pick it from all the others because it at least has a magical ring to it. Unlike Bob. Seriously, whats with Bob, Dave, and Steve? They are ok names... but not for a TREE. Especially a cool tree.
Bob may be nice, because of its shortness or simplicity, or whatever other reasons you pull up for it, but as (someone? sorry...) said, it is a metaphor for the common. It's a filthy name for a tree. I didn't vote, because the names offered aren't good enough.