Where does “четыре” come from?
четыре (Russian) comes from Old East Slavic четꙑре, from Proto-Slavic *četỳre, from Proto-Balto-Slavic ketures, from Proto-Indo-European kʷetwóres, from Proto-Indo-European kʷe- — and.
четыре (Russian): four
Ancestry of “четыре”, step by step