Doggie?

Gavin is babbling more and more these days. He can say "DaDa" and "MaMa". We also get "deedee" from time to time. One night this week, we would have sworn we heard "doggie." Not wanting to think too much of his sounds, we dismissed it. But after this morning, we're thinking maybe he does know "doggie."
He was sitting on the island in the kitchen with Dave's support. When Mason walked through the kitchen, Gavin looked right at Mason and said, "Doggie." Dave and I stared at each other in disbelief. Gavin continued to chat and wiggle. We couldn't get him to repeat it, but can't get him to say "DaDa" or "MaMa" on demand, either.
Gavin enjoys watching Mason. When Gavin is in his exersaucer, Mason always comes over to give G a few kisses. Gavin smiles widely when he sees Mason headed his way. We've taught Mason that he cannot step on a blanket laying on the floor. (Who says you can't teach an old dog new tricks?) But, Mason fudges a little so he can be close to Gavin while he plays on the blanket by laying down as close as he can to the blanket, sometimes pushing the blanket out of the way of his paw. These two are going to be inseparable later.
So, I guess now he knows all the members of the family. I wonder what he'll "say" next.