Where does “ѧзꙑкъ” come from?
ѧзꙑкъ (Old East Slavic) comes from Proto-Slavic ęzykъ, from Proto-Balto-Slavic inźūˀ-kas, from Proto-Balto-Slavic *inźūˀs, from Proto-Balto-Slavic *dinźūˀs, from Proto-Indo-European dn̥ǵʰwéh₂s — tongue.
Ancestry of “ѧзꙑкъ”, step by step