My daughter has always enjoyed playing around with names. I still remember when she realized that Apo and I have other names as well. She seemed to consider it the same as how she also has two names: the English and Slovak versions of her name. "I Katie and Katka! You Melissa and Mama!"
We use the same full version of her name everywhere - Katarína - but encourage English speakers who have trouble with the nickname - Katka - to call her Katie instead. I used to call her Katie myself, but once she started talking she showed a clear preference for Katka, so I decided to respect that...
So far fairly simple, but once you get further into nicknames it gets kind of hectic. Katarína (Katherine in English, Kateřina in Czech) comes with a ton of short versions. Katka becomes Katuška, Katuš, Kaťula, Kaťulka, Káťa, Káča, Kačka, Kačena, Kačenka...and those are just the common ones!
We use a range of nicknames (often entirely unrelated to her actual name) but usually Katka or Katuška. The most common nickname for little girls named Kateřina in Czech, though, is Kačenka. And by most common I mean people start calling you that automatically whether you like it or not. It's very Czech instead of Slovak, though, and the Slovak doesn't like it, so we never called K Kačenka at home...and therefore she never heard it until we moved six months ago.
I didn't really think about it as an issue until her teachers at the new school asked me what they should call K (they wanted something more little-girly than plain Katka) - "She doesn't even look up when we call her Kačenka!!" I explained that she probably didn't realize that was supposed to be her name, and explained that we usually use Katka or Katuška. They call her Katuška and related names now, which works out great for everyone.
Since then I've been paying attention and have noticed that K will actually answer to anything - EXCEPT Kačenka! Sometimes she ignores it completely, and other times she insists, "I NOT Kačenka!"
Yesterday I asked her if her name was Kačenka and she said, "I NOT Kačenka! Kačenka is kačenka. Duck. I not a duck."
This was the point where I fell on the floor laughing, because kačenka DOES mean duck, and that's the reason the Slovak doesn't like it: why would you call your little girl Duck? He's never mentioned that to K, but she apparently came to the same conclusion herself!
Our awesome little Katuška is not a duck...