i believe the term BCAA is widely associated with valine, leucine, and isoleucine in the body building world, but outside of that (rest of the world) the term branched chain of amino acids is a term referring to the unique branch-like chemical structure that the 3 amino acids form. this is not the only 3 amino acids that when bonded form a "branch chain" structure, but it by far the most common and overtime has generally been accepted as those 3. like peachfuzz, i was trying to be exact.
everything you read on Wikipedia may not be correct or the full story.