First words?

I'm not really sure how parents decide what their child's first words are.  Parker has been saying "Mama", "Dada", and "Yeah" for a long time, but they're only contextually appropriate about 80% of the time.

I know that he knows that I'm called "Mama" and Keith is "Dada", but I'm not convinced that he realizes that the rest of the world is not also called Mama or Daddada.

But, recently, whenever I put hand lotion on, Parker raises his hands to me, then rubs his hands together and says "rub, rub, rub".  He also says it when we're washing his hands, and when he takes the towel down to dry his hands.

Not really sure how it happened, but is it possible that "rub, rub, rub" is Parker's first word?

That is one funny kid.