Where does “supīnus” come from?

supīnus (Latin) comes from Proto-Indo-European upó, from Proto-Indo-European h₃ewp-.

Ancestry of “supīnus”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	upó	under, below
2	Proto-Indo-European	h₃ewp-	—

supīnus — Etymology, Origin & Word History | Etymology Explorer