Where does “culo” come from?

culo (Spanish) comes from Old Spanish culo, from Latin cūlus, from Proto-Celtic kūlos, from Proto-Indo-European ḱuH-ló-, from Proto-Indo-European (s)kewH- — to cover, bedeck; cover.

culo (Spanish): ass, arse, booty, rear, behind, butt, buttocks;...