Callisto

type of strong, fragrant herb found in Northern temperate zones, late 14c., calamente, from Old French calamente, from Medieval Latin calamentum, probably from Greek kalaminthē, name of an odoriferous plant, perhaps literally "beautiful mint" (kalos "beautiful, noble, good," see Callisto + minthē, see mint (n.1)). But Beekes writes that "The formal agreement ... does not permit a conclusion" and that a folk-etymology origin is equally hypothetical.

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, had the Greeks attempted such a word, would have been *kallistheneia.