Where does “стадо” come from?

стадо (Old Church Slavonic) comes from Proto-Slavic stàdo, from Proto-Indo-European steh₂-dʰo-m.

стадо (Old Church Slavonic): herd

Definitions

Step	Language	Word	Meaning
1	Proto-Slavic	stàdo	—
2	Proto-Indo-European	steh₂-dʰo-m	—

стадо — Etymology, Origin & Word History | Etymology Explorer