Where does “mega” come from?

Mega comes from Ancient Greek μέγας, derived from Proto-Indo-European meǵh₂s, both meaning great or large.

mega (English): Very large; great; excellent

Definitions

Step	Language	Word	Meaning
1	Ancient Greek	μέγας	big, large; great, mighty, loud; marvelous,...
2	Proto-Indo-European	meǵh₂s	great

mega — Etymology, Origin & Word History | Etymology Explorer