incestyoudaoicibaDictYouDict[incest 词源字典]
incest: [13] Etymologically, incest is virtually the same word as unchaste. It was borrowed from Latin incestus, a noun use of an adjective formed from the negative prefix in- and castus ‘pure’ (source of English chaste). The Latin word denoted ‘unchastity’ in general, but in practice was often applied specifically to ‘sexual contact between close relatives’.
=> chaste[incest etymology, incest origin, 英语词源]
incest (n.)youdaoicibaDictYouDict
c. 1200, "the crime of sexual intercourse between near kindred," from Old French inceste and directly from Latin incestum "unchastity, impious unchastity," also specifically "sex between close relatives," noun use of neuter adjective incestus "unchaste, impure," from in- "not" (see in- (1)) + castus "pure" (see caste). In early use also in reference to sexual relations or marriage with one under a vow of chastity (sometimes distinguished as spiritual incest). Old English had sibleger "incest," literally "kin-lying."