Where does “[[въ-]]” come from?

[[въ-]] (Old East Slavic) comes from Proto-Slavic vъ(n)-, from Proto-Indo-European h₁én — in.

Ancestry of “[[въ-]]”, step by step

StepLanguageWordMeaning
1Proto-Slavicvъ(n)-—
2Proto-Indo-Europeanh₁énin
Every word from Proto-Indo-European h₁én →Every word from Proto-Slavic vъ(n)- →