That's what I was thinking. Well, I'm a Mike W too.It is my initials. M.W.
I was on an email list with several Mikes. So we signed our posts as Mike W., Mike G., Mike F., etc. When George W. Bush arrived on the national political scene and people started referring to him as "Dubya" I adopted the m dubya moniker as tongue in cheek. It stuck and has been causing confusion ever since. 😁
I had many nicknames as a youth and as a young man, so, m dub, or dubby, dubya seemed like a good and natural progression into a more grown up, yet still informal, nickname.