The many meanings of “up”

Jack says “up” a LOT, and the word keeps getting new meanings (without getting rid of the old ones).  It started out just meaning “pick me up”.  Then, sometimes “up” meant “move, please” or “get out of my way”.  Next, “up” started to mean “down”, as in “put me down” or “I want to get down” if he was already up.  (And if he says “up” and you say, “do you mean down?”, he’ll say “yup”.  He just won’t attempt to say down.)  After that, “up” could also mean “on top of” something or “higher than something else”.  Like, he’ll lift the ladder on top of his fire truck and say “up”, or he’ll stack a toy on top of another toy and say “up”.  Most recently, like new yesterday, Jack looked at John, pointed next to him on the rug, and said “up”.  He very clearly meant “sit down right here, Dad.”  A couple hours later, he was sitting in the big gray chair and he did the same thing to me.  Pointed to the cushion and said “up.”  So I sat down next to him in the chair, and he was happy.

(Up is a super weird-looking tiny word.)