Where does “четвертий” come from?
четвертий (Ukrainian) comes from Old East Slavic четвьртъ, from Proto-Slavic četvьrtъ, from Proto-Balto-Slavic ketwirtas, from Proto-Indo-European *kʷetwr̥tós.
четвертий (Ukrainian): fourth
Ancestry of “четвертий”, step by step