My friends in school called me Owl because it was my favorite animal. Then we started writing a book series together (I'm talking 100+ pages per book, not short stories) and we all made characters based on ourselves. A couple of our character names stuck as nicknames for a few years. Mine was Naunakhte, Nauna for short.
One of them still calls me Nauna on rare ocassion, and my closest friends that I knew since HS will still call me Owl once in a while, and we still refer to my other friends sometimes as Wolf, and Fox or Mama fox (she liked to act like our mother figure in school as she was the oldest by a few months, in adulthood, however, she is the farthest thing from maternal or mother like as you can get, lol)