This word appears to have undergone several changes throughout its hisory. Can someone enlighten me as to how the term, which meant "naked place" in ancient Greece, came to mean an intellectual facility in 15th C. German language, to an athletics-only (but somewhat clad) facility in its modern iteration? Does the expression, "mental gymnastics" harken to the old Germanic term, or is it a modernism?

Hmmm, good question, Geoff. Perhaps this link from Etymology.com is helpful. From the 1590s, it said, it's from the Latin word gymnasium, from the Greek gymnasion, for "a public place where athletics is practiced." Indeed, it then says it later included training for the mind.