Where does “γυμνάσιον” come from?

γυμνάσιον (Ancient Greek) comes from Ancient Greek γυμνάζω, from Ancient Greek γυμνός, from Proto-Hellenic *gʷomnós.

γυμνάσιον (Ancient Greek): bodily exercises; gymnastic school, school

Definitions

Step	Language	Word	Meaning
1	Ancient Greek	γυμνάζω	to train naked; to train
2	Ancient Greek	γυμνός	naked, nude, unclad; unarmed, without armor,...
3	Proto-Hellenic	*gʷomnós	—

γυμνάσιον — Etymology, Origin & Word History | Etymology Explorer