Where does “stynja” come from?

stynja (Old Norse) comes from Proto-Germanic stunjaną, from Proto-Germanic stenaną, from Proto-Indo-European (s)tona-.

Ancestry of “stynja”, step by step

Step	Language	Word	Meaning
1	Proto-Germanic	stunjaną	to sound, crash, bang, groan
2	Proto-Germanic	stenaną	to sigh, to groan
3	Proto-Indo-European	(s)tona-	—

stynja — Etymology, Origin & Word History | Etymology Explorer