That’s such an interesting question. I do like nicknames. Often the story behind the nickname is entertaining or illuminating. I use nicknames in my books with some regularity. Often, a character does not have a clear understanding of who he or she is. A nickname is one of the tools in a writer’s toolbox. A nickname can help the reader learn more about the character, sometimes more than the character knows about her or himself.
I don’t believe I had a real nickname as a child. But my family has affectionately called me “fog” over the years because, I think, sometimes I’m not entirely visible to them.