c. 1200, chastete, "sexual purity" (as defined by the Church), including but not limited to virginity or celibacy, from Old French chastete "chastity, purity" (12c., Modern French chasteté), from Latin castitatem (nominative castitas) "purity, chastity" from castus "cut off, separated; pure" (see caste). Chastity-belt is from 1894 (belt of chastity is from 1878).
Chastity is merely a social law created to encourage the alliances that most promote the permanent welfare of the race, and to maintain woman in a social position which it is thought advisable she should hold. [Saturday Review, Aug. 10, 1867, quoted in Lecky, "European Morals," 1869]