I'm never sure of my own name anymore. Some groups I belong to have another member named Janet, so they call me Jan. Other groups have someone named Jan, so I'm Janet to them.
When I was a kid in the 1940s I asked my parents to call me Jan, but everybody "knew" that was a boy's name in Holland, so it wasn't appropriate for a girl. I suggested that they call me Jenny, but that was the name of a mule in a comic strip so nobody would want to be called by that name.
I was stuck with being called Janet until the day I got married. But Janet Collins seemed a little bit difficult to pronounce because of the "t" and "C" sounds being next to each other, so some people started calling me Jan. By then people didn't think of it as a boy's name.
Centuries ago a nick name was originally an eke name.
Eke meant just a tiny bit more, like eking out something. If someone was affectionate they'd add something tiny to show that at the end of a person's name. For example John would be called Johnny, or George would have the nickname of Georgie. Those are diminutives and show affection.
Of course many nicknames are shorter than the original names. Will is shorter than William and Sue is shorter than Sue, but Billy and Susie are still used.
And lots of nicknames aren't based on the original names at all. People may be called affectionate things like Sugar, Sweetie, or Honey or called by their relationship to others or some noticeable characteristic. I've known people called Sis, Sonny, Red, and Doc, among others.
Do you have a nickname?
If you do, do you like having it?