unnatural (adj.)youdaoicibaDictYouDict[unnatural 词源字典]
early 15c., "not in accord with physical nature," from un- (1) "not" + natural (adj.). Meaning "artificial" is attested from 1746; that of "at variance with moral standards" is from 1520s. Related: Unnaturally; unnaturalness.[unnatural etymology, unnatural origin, 英语词源]