Where does “bruś/k-” come from?

bruś/k- (Proto-Balto-Slavic) comes from Proto-Indo-European bʰruḱ-.

Ancestry of “bruś/k-”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	bʰruḱ-	—

bruś/k- — Etymology, Origin & Word History | Etymology Explorer