Where does “czwarty” come from?

czwarty (Polish) comes from Old Polish cztwarty, from Proto-Slavic četvьrtъ, from Proto-Balto-Slavic ketwirtas, from Proto-Indo-European *kʷetwr̥tós.

czwarty (Polish): fourth

Definitions

Step	Language	Word	Meaning
1	Old Polish	cztwarty	fourth
2	Proto-Slavic	četvьrtъ	fourth
3	Proto-Balto-Slavic	ketwirtas	fourth
4	Proto-Indo-European	*kʷetwr̥tós	—

czwarty — Etymology, Origin & Word History | Etymology Explorer