formality (n.)youdaoicibaDictYouDict[formality 词源字典]
1530s, "agreement as to form," from formal + -ity or else from Middle French formalité (15c.) or Latin formitalitatem. Sense of "conformity to established rule" is from 1590s; meaning "something done for the sake of form" is from 1640s. Related: Formalities.[formality etymology, formality origin, 英语词源]