Where does “oxymorum” come from?

oxymorum (Latin) comes from Ancient Greek ὀξύμωρος, from Ancient Greek μωρός, from Proto-Indo-European muHrós — dull, stupid.

Ancestry of “oxymorum”, step by step

Step	Language	Word	Meaning
1	Ancient Greek	ὀξύμωρος	pointedly foolish; oxymoronic
2	Ancient Greek	μωρός	slow, sluggish; slow, dull, foolish, stupid;...
3	Proto-Indo-European	muHrós	dull, stupid

oxymorum — Etymology, Origin & Word History | Etymology Explorer