Where does “вьчера” come from?
вьчера (Old Church Slavonic) comes from Proto-Slavic vьčera, from Proto-Slavic večerъ, from Proto-Balto-Slavic wékeras, from Proto-Indo-European wekʷsperos.
вьчера (Old Church Slavonic): yesterday
Ancestry of “вьчера”, step by step