When you are born your parents give you a name. For some it takes many hours to determine what that name should be. Some want it to reflect family heritage. Some want it to be connected to popular culture, based on some famous book, TV or movie character. Some just like the way it sounds. For whatever reason, you are given a name that your parents want you known by. Then you grow up and your name gets personalized. Your name becomes the unique identifier of you. In some cases decided by some and accepted by everyone. In some chosen only to be used by select groups. In some cases you choose it yourself.
For some it is just a shortening of your name. Jonathan becomes John, Christina becomes Tina, Elizabeth becomes Beth or Liz, etc. For others it is a true nickname. George Herman Ruth became the Babe, Doctor Leonard McCoy became Bones, Djeliba Baba becomes Baba the Storyteller, to name a few.
When I generally interact with people I shorten everyone’s first name, I refer to my son David as D, my niece Alison as Ali, Michael – Mike, Rachel – Rache. My name shortened would be Harv and no one refers to me as that. My first name does not lend itself to many options. With a given name like Harvey, most people call me Harvey.