Where does “ivierno” come from?

ivierno (Old Spanish) comes from Latin hībernum, from Latin hībernus, from Proto-Indo-European ǵʰey- — winter.

Ancestry of “ivierno”, step by step

Step	Language	Word	Meaning
1	Latin	hībernum	—
2	Latin	hībernus	—
3	Proto-Indo-European	ǵʰey-	winter

ivierno — Etymology, Origin & Word History | Etymology Explorer