Where does “štwórtk” come from?
štwórtk (Upper Sorbian) comes from Proto-Slavic četvьrtъkъ, from Proto-Slavic četvьrtъ, from Proto-Balto-Slavic ketwirtas, from Proto-Indo-European *kʷetwr̥tós.
štwórtk (Upper Sorbian): Thursday
Ancestry of “štwórtk”, step by step