Where does “мегаполис” come from?

мегаполис (Russian) comes from Ancient Greek μέγας, from Proto-Indo-European meǵh₂s — great.

Ancestry of “мегаполис”, step by step

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

мегаполис — Etymology, Origin & Word History | Etymology Explorer