"oh yeah"

He's talking! if  saying "oh yeah" counts as talking- ha ha! He has said this phrase more consistently than he has said anything else. I guess it counts as his first word. He usually says it in response to a question like "Aiden, do you want some yogurt?" or "Aiden, do you want to go outside?". He'll also just say it randomly when he's walking through the house. He says it when he finds some goldfish on the table. It is so funny!
I am clueless as to where it came from. Neither Jeff nor I use the phrase. Aiden came up with it all on his own. I work with him almost daily on saying "mama", "ball", "cup" and some other easy words. Obviously, he's going to say what he wants to.
He says "Da-da" pretty often, but I'm not sure the association is there yet. He knows who Da-da is, but he doesn't always say it around him or to address him. "oh yeah" is more often and in response to questions.
I am trying my best to get it on video.