rezavý (Czech) comes from Proto-Slavic rъďavъ, from Proto-Slavic rъďa, from Proto-Slavic rudъ, from Proto-Balto-Slavic roudos, from Proto-Indo-European h₁rowdʰ-o-, from Proto-Indo-European h₁rewdʰ- — red.
rezavý (Czech): rusty