Where does “szczyry” come from?

szczyry (Old Polish) comes from Proto-Slavic ščirъ, from Proto-Indo-European (s)kei̯ro-.

Ancestry of “szczyry”, step by step

Step	Language	Word	Meaning
1	Proto-Slavic	ščirъ	blite; mercury; sincere, frank
2	Proto-Indo-European	(s)kei̯ro-	—

szczyry — Etymology, Origin & Word History | Etymology Explorer