Where does “cztwierć” come from?

cztwierć (Old Polish) comes from Proto-Slavic četvьrtь, from Proto-Slavic četvьrtъ, from Proto-Balto-Slavic ketwirtas, from Proto-Indo-European *kʷetwr̥tós — fourth.

Ancestry of “cztwierć”, step by step

StepLanguageWordMeaning
1Proto-Slavicčetvьrtь—
2Proto-Slavicčetvьrtъfourth
3Proto-Balto-Slavicketwirtasfourth
4Proto-Indo-European*kʷetwr̥tósfourth
Every word from Proto-Indo-European *kʷetwr̥tós →Every word from Proto-Balto-Slavic ketwirtas →Every word from Proto-Slavic četvьrtъ →