Wilhelm is a name by oldest sister has used for me in a loving fashion. I like it because it is dignified. My full name is James William, but I have always gone by Billy. I don't use James, because my father and older brother both are James W., and that would have been confusing. My younger brother is Charles James, so he got to use his first name.
Over the course of my life it has been suggested to me that Billy is a diminutive name; but I prefer it all the same. William is just too refined, and Bill is too short, however I don't mind if people call me Bill. But I prefer Billy, or if you're my oldest sister you can get away with Wilhelm.