Where does “ya” come from?

ya (Mednyj Aleut) comes from Russian я, from Old Church Slavonic ꙗзъ, from Proto-Slavic (j)azъ, from Proto-Balto-Slavic ēź-, from Proto-Indo-European éǵh₂ — I.

Ancestry of “ya”, step by step

StepLanguageWordMeaning
1RussianяI first-person singular subject pronoun
2Old Church Slavonicꙗзъ—
3Proto-Slavic(j)azъI
4Proto-Balto-Slavicēź-—
5Proto-Indo-Europeanéǵh₂I
Every word from Proto-Indo-European éǵh₂ →Every word from Proto-Balto-Slavic ēź- →Every word from Proto-Slavic (j)azъ →