Where does “акмеизм” come from?

акмеизм (Russian) comes from Ancient Greek ἀκμή, from Proto-Indo-European h₂eḱ- — sharp.

Ancestry of “акмеизм”, step by step

Step	Language	Word	Meaning
1	Ancient Greek	ἀκμή	point, edge; the highest or culminating point of...
2	Proto-Indo-European	h₂eḱ-	sharp

акмеизм — Etymology, Origin & Word History | Etymology Explorer