calisthenics (n.)

also callisthenics, kind of light gymnastics, 1842, (the adjective calisthenic/callisthenic, of exercises, was in use by 1837), formed on model of French callisthenie, from Latinized combining form of Greek kallos "beauty" (see Callisto) + sthenos "strength, power, ability, might" (perhaps from PIE root *segh- "to have, hold," on the notion of "steadfastness, toughness") + -ics.

"Of this at least I am certain, that none but a born romp and hoyden, or a girl accustomed [to] those new-fangled pulleyhauley exercises, the Calisthenics, is fitted for the boisterous evolutions of a sea-voyage." [Thomas Hood, "The Schoolmistress Abroad," New Monthly Magazine, 1842]

Originally, gymnastic exercises suitable for girls and meant to develop the figure and promote graceful movement. OED describes the word as "chiefly a term of young ladies' boarding-schools." A place for doing it was a calisthenium (1853). The proper Greek, if there was such a word in Greek, would have been *kallistheneia.