Tomorrow is my name day

A colleague came and told me, that it is my name day Tomorrow. He was quite disappointed that I didn't know, because down here name day or "onomastico" is regarded as a bit of a birthday, which means cake day for the colleagues.
I looked at bit around and found that Kim, was in fact the name day in Norway (link). But here in Italy its a celebration of the saint with the corresponding name, more than the person who wears the name. So since Norway and Sweden are not catholic countries and therefore don't believe in saints, I wonder why they celebrate it.

I did some more searching and found that in Denmark "Kim" is a common name (that I knew already ;-)) but that it had a big renaissance after World War II because of the resistance man called Kim Malthe-Bruun.(link).

I asked my dad, if that was why I was called Kim (not that I am that old), but he answered "jeg kan ikke huske hvorfor du skulle hedde kim, men se praktisk på det, det er kort og alle kan nogenlunde sige det internationalt"
which means "I don't remember, but it's practical"