Where does “apert” come from?

apert (Old French) comes from Latin apertus, from Latin aperiō, from Proto-Indo-European h₂epó — off, away.

Ancestry of “apert”, step by step

Step	Language	Word	Meaning
1	Latin	apertus	opened, open, free; public; having been opened;...
2	Latin	aperiō	—
3	Proto-Indo-European	h₂epó	off, away

apert — Etymology, Origin & Word History | Etymology Explorer