"Of or relating to dancing; specifically of, belonging to, or designating a dance sequence performed by a chorus in classical theatre", Early 18th cent.; earliest use found in John Weaver (1673–1760), dancer and choreographer. From post-classical Latin orchesticus and its etymon ancient Greek ὀρχηστικός of or relating to dancing from ὀρχηστής dancer (from ὀρχεῖσθαι to dance + -της, suffix forming agent nouns) + -ικός.[orchestic etymology, orchestic origin, 英语词源]