Where does “ша” come from?

ша (Serbo-Croatian) comes from Serbo-Croatian шта, from Proto-Slavic čьto, from Proto-Balto-Slavic ki, from Proto-Indo-European kʷíd, from Proto-Indo-European kʷís, from Proto-Indo-European kʷi- — interrogative base.

Ancestry of “ша”, step by step

StepLanguageWordMeaning
1Serbo-Croatianштаwhat
2Proto-Slavicčьtowhat
3Proto-Balto-Slavickiwhat
4Proto-Indo-Europeankʷídneuter nominative/accusative singular of *kʷís
5Proto-Indo-Europeankʷíswho, what; who, which, that; which, what
6Proto-Indo-Europeankʷi-interrogative base
Every word from Proto-Indo-European kʷi- →Every word from Proto-Indo-European kʷís →Every word from Proto-Indo-European kʷíd →