Comment by danans

> I'm not a linguist so I can't send any articles that explain the origins of this mess.

It's probably because Polish, unlike English and most Western European languages, has a case system (where nouns are modified to indicate their function, i.e subject, object, instrument, etc).

That's a pretty common feature in grammatically conservative Indo-European languages. Other living Indo-European languages, like Lithuanian, are even more conservative and have preserved nearly the entire case system of their ancestor.