Where does “Баба-яга” come from?

Баба-яга (Russian) comes from Proto-Slavic baba ęga, from Proto-Balto-Slavic bā́ˀbāˀ inˀgāˀ.

Ancestry of “Баба-яга”, step by step

Step	Language	Word	Meaning
1	Proto-Slavic	baba ęga	Baba Yaga; old witch, hag
2	Proto-Balto-Slavic	bā́ˀbāˀ inˀgāˀ	—