chaste: [13] Chaste comes via Old French from Latin castus ‘pure’. The notion of making someone pure, by correcting or reproving them, was expressed in Latin by the derived verb castīgāre, which passed into English in the 17th century as castigate. Old French, however, had already adopted it as chastier, which in the 12th century produced the now obsolete English verb chaste ‘discipline’. From it were formed the derivatives chastise [14] and chasten [16]. Also ultimately from Latin castus is English caste. => caste, chasten, chastise, incest
chaste (adj.)
c. 1200, "virtuous, pure from unlawful sexual intercourse" (as defined by the Church), from Old French chaste "morally pure" (12c.), from Latin castus "clean, pure, morally pure" (see caste). Transferred sense of "sexually pure" is by 15c., perhaps by influence of chastity, though chaste as a noun meaning "virgin person" is recorded from early 14c. Related: Chastely.