1561, from Gk. khoros "band of dancers or singers, dance, dancing ground," from PIE *ghoro-. In Attic tragedy, the khoros gave expression, between the acts, to the moral and religious sentiments evoked by the actions of the play. Originally used in theatrical sense; meaning of "a choir" first attested 1656. Meaning "the refrain of a song" (which the audience joins in singing) is 1599. Chorus girl is 1894.