moralyoudaoicibaDictYouDict[moral 词源字典]
moral: [14] Latin mōs ‘custom’ is the starting point of the English family of ‘morality’-words (and its plural mōres was acquired by English as mores in the 20th century). Its derived adjective mōrālis was coined, according to some by Cicero, as a direct translation of Greek ēthikós ‘ethical’, to denote the ‘typical or proper behaviour of human beings in society’, and was borrowed directly into English in the 14th century. Morale [18] was borrowed from French, where it is the feminine form of the adjective moral.

At first it was used in English for ‘morality, moral principles’; its modern sense ‘condition with regard to optimism, cheerfulness, etc’ is not recorded until the early 19th century.
=> morale, mores[moral etymology, moral origin, 英语词源]
moral (adj.)youdaoicibaDictYouDict
mid-14c., "pertaining to character or temperament" (good or bad), from Old French moral (14c.) and directly from Latin moralis "proper behavior of a person in society," literally "pertaining to manners," coined by Cicero ("De Fato," II.i) to translate Greek ethikos (see ethics) from Latin mos (genitive moris) "one's disposition," in plural, "mores, customs, manners, morals," of uncertain origin. Perhaps sharing a PIE root with English mood (n.1).

Meaning "morally good, conforming to moral rules," is first recorded late 14c. of stories, 1630s of persons. Original value-neutral sense preserved in moral support, moral victory (with sense of "pertaining to character as opposed to physical action"). Related: Morally.
moral (n.)youdaoicibaDictYouDict
"moral exposition of a story," c. 1500, from moral (adj.) and from French moral and Late Latin morale.