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