Where does “of-” come from?

of- (Middle English) comes from Old English of-, from Proto-Germanic aba-, from Proto-Indo-European h₂epó — off, away.

Ancestry of “of-”, step by step

Step	Language	Word	Meaning
1	Old English	of-	off, away, from, out of, away from; down;...
2	Proto-Germanic	aba-	away, away from
3	Proto-Indo-European	h₂epó	off, away

of- — Etymology, Origin & Word History | Etymology Explorer