I've a feeling that Tommy Daniel may not be a suitable case, in that Daniel was a surname. I have known a few by that surname, though Daniels is more common. This is in northern England, I didn't know Tommy, but that has been my understanding as long as I knew of him.

I did know a Karl Francis (first names) when much younger, his younger brothers also had two names apiece, but only he was regularly addressed by both names. The family were of mixed origin (aren't we all) a Swiss/Jewish-refugee X gentile-Edinburgh cross. Not sure how this affects the theory, but all data is relevant??