So has the origin of the Phoenix ever been established?

I don’t remember reading where the Phoenix came from that was part of the Avengers B.C.. Is it possible that she was the Iron Fist that became the host of the Phoenix force in the New Avengers storyline during AvX? That could be an interesting twist.

How awesome would it be if they revealed that she had a child with Odin? She could be an Asgardian, with the Phoenix Force, who possibly could attain the Iron Fist. That would be insane! Angela could even fit into being that character.

I ultimately posted this here because the X-Men are the reason I even read comics.