Where does “беспримјеран” come from?

беспримјеран (Serbo-Croatian) comes from Serbo-Croatian без, from Proto-Slavic bez, from Proto-Indo-European *bʰeǵʰs.

Ancestry of “беспримјеран”, step by step

Step	Language	Word	Meaning
1	Serbo-Croatian	без	without, excluding, not counting; linen, canvas;...
2	Proto-Slavic	bez	without
3	Proto-Indo-European	*bʰeǵʰs	—

беспримјеран — Etymology, Origin & Word History | Etymology Explorer