Where does “boier” come from?

boier (Romanian) comes from Romanian boiarin, from Old Church Slavonic болꙗринъ, from Proto-Slavic bojь, from Proto-Indo-European bʰoyh₂ós, from Proto-Indo-European bʰeyh₂- — to fear, be afraid; to strike, hit; to hew, cut.

boier (Romanian): boyar (a form of nobility or aristocracy), landowner, magnate