Where does “язъ” come from?

язъ (Ukrainian) comes from Old East Slavic ꙗзъ, from Proto-Slavic (j)azъ, from Proto-Balto-Slavic ēź-, from Proto-Indo-European éǵh₂ — I.

Ancestry of “язъ”, step by step

StepLanguageWordMeaning
1Old East SlavicꙗзъI
2Proto-Slavic(j)azъI
3Proto-Balto-Slavicēź-—
4Proto-Indo-Europeanéǵh₂I
Every word from Proto-Indo-European éǵh₂ →Every word from Proto-Balto-Slavic ēź- →Every word from Proto-Slavic (j)azъ →