Where does “Oktaeder” come from?

Oktaeder (German) comes from Ancient Greek ἕδρα, from Proto-Hellenic *hédrā.

Oktaeder (German): octahedron

Definitions

Step	Language	Word	Meaning
1	Ancient Greek	ἕδρα	seat, chair, stool, bench; the act of sitting;...
2	Proto-Hellenic	*hédrā	—

Oktaeder — Etymology, Origin & Word History | Etymology Explorer