Where does “волъ” come from?

волъ (Old East Slavic) comes from Proto-Slavic volъ, from Proto-Balto-Slavic walas.

Ancestry of “волъ”, step by step

StepLanguageWordMeaning
1Proto-Slavicvolъox
2Proto-Balto-Slavicwalas—
Every word from Proto-Balto-Slavic walas →Every word from Proto-Slavic volъ →