@NikeBG Niki is more feminine than masculine in Slovak. I wouldn’t be surprised if a boy would be called Niki, but boys generally call themselves Niko. Although Miki (from Mikuláš) is always a masculine form. Edit: Apparently there’s a feminine name Mikuláška, so it would apply to her as well.
Just now I found out that in Slovakia, Nikola is both feminine and masculine. I’m surprised, because I thought it’s only feminine. I’ve never knew about any Slovak named Nikola.
In Slovak calendar, Nikola and Nikolaj name day is 29.8. and Mikuláš, Niko and Nikolas name day is 6.12. Nikoleta has 2 name days. I don’t understand it.