Many years ago, I signed up for an excite account under the name michaelpate. I played with it a couple of times and then didn’t return for month. When I came back, try as I might, I could not figure out the password. So I signed up for a new account as michaelkpate. And I have pretty much always used that username ever since.
I also make it a practice to register it on as many services as possible that I might ever want to use. But if you have a variety of usernames various places (and you want people to know how they interconnect, then onXiam is probably just what you are looking for.