gymnasiumyoudaoicibaDictYouDict[gymnasium 词源字典]
gymnasium: [16] Greek gumnós meant ‘naked’. It was customary in ancient times for athletes to train naked, and so the verb gumnázein came to mean ‘train, practise’ – particularly by doing exercises (whence English gymnast [16]). From the verb was derived the noun gumnásion, which Latin borrowed as gymnasium ‘school’. This academic sense has never caught on to any extent in English (although it is the word’s only application in German); we have preferred to go back to the original athletic connotations.
[gymnasium etymology, gymnasium origin, 英语词源]
gymnasium (n.)youdaoicibaDictYouDict
1590s, "place of exercise," from Latin gymnasium "school for gymnastics," from Greek gymnasion "public place where athletic exercises are practiced; gymnastics school," in plural, "bodily exercises," from gymnazein "to exercise or train," literally or figuratively, literally "to train naked," from gymnos "naked," from a metathesis of PIE *nogw-mo-, suffixed form of *nogw- "naked" (see naked).

A feature of all ancient Greek communities, at first it was merely an open space, later with extensive facilities and including training for the mind as well as the body. Hence its use in German from 15c. as a name for "high school" (more or less paralleling a sense also in Latin); in English it has remained purely athletic. For the "continental high school sense," English in 19c. sometimes used gymnastical as an adjective, gymnasiast for a student.