Where does “чисто̀ћа” come from?
чисто̀ћа (Serbo-Croatian) comes from Serbo-Croatian чи̏ст, from Proto-Slavic čistъ, from Proto-Balto-Slavic skīstas, from Proto-Indo-European skidtos, from Proto-Indo-European (s)keyd-.
Ancestry of “чисто̀ћа”, step by step
Words derived from “чисто̀ћа”