There's no any. But rzecz can be used for an abstractive thing, przedmiot not.
What about "teges"? Other than it being more informal/slang, is there a difference in meaning/usage with rzecz and przedmiot?
Teges is used used more for something we don't know how to call otherwise (in slang of course, as you correctly noticed, but the kind of slang used by people who are already a couple decades old). Might be used in some phrases like „ten teges” ("this thingy"), „nie ten teges” ("dumb" about a person) or „teges-szmeges” ("some stuff" that was told).
It's not used for mentioning a thing in general context („rzecz” is already perfectly fitting for that even in casual context).
This is amazing when you think of swedish föremål: both start with 'front' (and no idea about miot)
Another one I like is the Italian perché and the Polish dlaczego. Both start with "for" and end with "what". I'm sure other languages fit in too, the Swedish värför is kinda similar.
In Hebrew as well, why = למה
Mål means goal, language (from mäla - to say), meal and maybe some other meanings that I don't know.
Take your pick. I would hazard that it has to do with "mäla". Like something that has been said or named beforehand. This is just speculation on my part though.
"ten" doesn't really mean "that", but Polish and English perceive the 'closeness' of an object differently.
So in Polish you have "ten/ten/tamten" and in English you have "this/that/that". So the second "ten" and first "that" overlap.
In (UK) English:
this/these: object(s) within arm's reach;
that/those: object(s) I can't touch without standing up.
Well, "książ" isn't really a word, apart from "Książ" being a district in Wałbrzych and a castle.
But you have "książę" (prince). Still, I don't really know if they're related... I think not.
Perhaps they somehow are related, but I couldn't find good sources on that. Maybe it had something to do with the fact that the ability to read was not common in early medieval times and only certain individuals, like rulers or priests could do that.