There are those who call me … Mike.
and my real name is Nancy.
Wow, I had no idea so many people went by other names. I’ve used my middle name on occasions I don’t want people to know my real name, like in clubs, but never assumed I could get away with it in everyday life.
Maybe I’ll start going by Luna 
…her name was Magill, but she called herself Lil, and everyone knew her as Nancy…
And then there was the guy named Clarence, who went by Chris. Now Chris might, I s’pose, with a little stretching, be seen as some kind of an offshoot of Clarence, but he got it from an uncle by way of an older brother. The brother spent the summer with the uncle and while he was there people started calling him “Little Chris” and the uncle “Big Chris”. When brother got home he was just Chris and Clarence (the little brother) was Christy. Somehow it stuck with little brother but got shortened to Chris, and that’s what he used as an adult, at least at work and such places. (I don’t really blame him, considering his given first and middle names).
He has a grandson whose name is John, but we call him Doug. (Of course, his middle name is Douglas.) I’m not sure how many people know that, though.
Other than that we don’t really go in much for nicknames in my family. I don’t really know why. Short forms, but not actual nicknames.
I have the same set of names as my father. So I have been called by my middle name since before I was born. In fact I am so unused to being referred by my first name, when someone does it, it just feels weird .
The advantage of this is that when I get a phone call asking for firstname lastname, I know it’s somebody I don’t want to talk to, like a telemarketer.
And my grandmother’s given name was Kathleen. So she was called Jimmy her entire life. Not surprising that she got a nickname, since most of the women on that side of the family are named Kathleen, but Jimmy?