Where does “сѧ” come from?

сѧ (Old East Slavic) comes from Proto-Slavic sę, from Proto-Balto-Slavic *sen, from Proto-Indo-European swé — self.

Ancestry of “сѧ”, step by step

StepLanguageWordMeaning
1Proto-Slavicsęoneself: myself, yourself, himself, herself,...
2Proto-Balto-Slavic*senoneself
3Proto-Indo-Europeanswéself

Words derived from “сѧ”

Every word from Proto-Indo-European swé →Every word from Proto-Balto-Slavic *sen →Every word from Proto-Slavic sę →
сѧ — Etymology, Origin & Word History | Etymology Explorer