Therapeutic
mid 17th century: via modern Latin from Greek therapeutikos, from therapeuein ‘minister to, treat medically’.
wiktionary
From New Latin therapeuticus(“curing, healing”), from Ancient Greek θεραπευτικός(therapeutikós, “attentive, helpful, obliging, curative”), from θεραπευτής(therapeutḗs, “one who waits on another, an attendant”), from θεραπεύω(therapeúō, “I wait on, attend, serve, cure”).
etymonline
therapeutic (adj.)
pertaining to the healing of disease, 1640s, from Modern Latin therapeuticus "curing, healing," from Greek therapeutikos, from therapeutein "to cure, treat medically," primarily "do service, take care of, provide for," of unknown origin, related to therapon "attendant." Therapeutic was used from 1540s as a noun meaning "the branch of medicine concerned with treatment of disease." Related: Therapeutical (c. 1600).