Where does “сабой” come from?

сабой (Belarusian) comes from Proto-Slavic *sobojǫ — (with) oneself, each other.

Ancestry of “сабой”, step by step

StepLanguageWordMeaning
1Proto-Slavic*sobojǫ(with) oneself, each other
Every word from Proto-Slavic *sobojǫ
сабой — Etymology, Origin & Word History | Etymology Explorer