Where does “коса́рь” come from?
коса́рь (Russian) comes from Russian -а́рь, from Proto-Slavic -ařь, from Gothic -𐌰𐍂𐌴𐌹𐍃, from Proto-Germanic -ārijaz, from Latin -ārius, from Proto-Italic *-āzios.
Ancestry of “коса́рь”, step by step
Words derived from “коса́рь”