I had a few nicknames growing up: Sam, Karinsky, Tinkerbell...
Each originated from a different source.
Sam came courtesy of my maternal Grandfather. It seems I watched too much Bewitched as a child and he called me Sam after the lead character. Oh, how I wished I could twitch my nose and do magic just like she did!
Karinsky, I'm told, came courtesy of my father's Polish barber. I'm not sure how much truth there is in that, though. You see, my father's always been quite the storyteller so there's always been a fine line between truth and fiction with his stories.
Tinkerbell was courtesy of my 7th grade teacher, Mr. George. He had previously taught my older brother and sister and we each got the nickname when going through his class. Mr. George was a large presence in the classroom with a big booming voice; you could say he commanded respect (or placed fear in his students!). In my young mind, he was kind of scary and could call me whatever he wanted!
There there's Kare. Family and friends usually end up calling me Kare at some point; much in the same way you'd say Lor(i), Shell(ey), or Jacq(ueline). After a while, I would start signing cards and letters that way as a sign of affection or, at the very least, comfortable familiarity.
These days I'll take either: Kare or Karen. Chances are good, if I'm meeting you for the first time I will introduce myself as Karen but soon afterwards will sign off my emails as Kare. Because now we're comfortable, familiar, and perhaps even friends.