In terminology, moral (TR:627), as contrasted with “immoral” (TR:44), from Latin moralis "proper behavior of a person in society," literally "pertaining to manners," coined by Cicero (“On Fate”, 45BC) to translate Greek ethikos (see: ethics); from Latin mos (genitive moris) "one's disposition," akin to "mores, customs, manners", related to or from the past participle of Latin mori ‘to die’, symbolized by the arrival of Mor, the Greco-Roman goddess of death. [1]

Etymology
The etymology of the term "moral", as a specific term, is generally accredited to Roman scholar Cicero, said to have coined the term in his 45BC work "On Fate", conceptualized as an equivalent of the Greek term ethics; the opening section of which reads as follows: [2]

“That branch of philosophy which, because it relates to manners, the Greeks usually term ethics [from: ήθος or ‘ethos’], the Latins have hitherto called the philosophy of manners. But it may be well for one who designs to enrich the Latin language, to call it moral science. And here we have to explain the nature and force of certain propositions which the Greeks term ‘axioms’. When these propositions relate to the future, and speak of possibilities and impossibilities, it is difficult to determine their precise force. Such propositions necessarily refer to the amount of possibility, and are only resolvable by logic, which I call the art of reasoning.”

This would seem to define moral science, according to Cicero, as the study of actions of behaviors that lead to death (or the arrival of Mor), and or the avoidance of such actions or behaviors.

This, seemingly, would trace the etymology of "moral" to Aristotle, and his "On Ethics", and likewise to his predecessors: Socrates, Plato, etc ; this etymology, however, remains to be elaborated on.

American writer Thomas Miller (2003), to elaborate, speculates that Cicero coined the Latin term for moral when he translated ethikos as moralis in “order to distinguish practical philosophy from speculative and natural philosophy.” [3]

Quotes
The following are related quotes:

“You don’t need religion to have morals. If you can’t determine right from wrong then you lack empathy, not religion.”
Anonymous (c.2001), CultureOfEmpathy.com (Ѻ)

“A theory of thermodynamics is not, and never will be, a moral theory. By moral theory, I mean, at the simplest level, any sustained attempt to give an account of how moral agents ought to live and act.”
Robert Louden (1992), Morality and Moral Theory [4]

See also
Moral landscape
Moral movement
Moral symbols
Morality

References
1. (a) Mor (mythology) – Wikipedia.
(b) Moral – Online Etymology Dictionary.
2. Cicero, M.T. (45BC). “On Fate”. Publisher; in: The Treatises of M.T. Cicero: On the Nature of Gods; On Divination; On Fate; On the Republic on the Laws; and On Standing for the Consulship (translator: C.D. Yonge) (§3:264-82). George Bell & Sons, 1878.
3. Miller, Thomas P. (2003). “Changing the Subject” (pg. 79), in: The Realms of Rhetoric (editors: Joseph Petraglia, Deepika Bahri). SUNY Press.
4. (a) Louden, Robert B. (1992). Morality and Moral Theory: a Reappraisal and Reaffirmation (thermodynamics, pgs. 96, 139). Oxford University Press.
(b) What Should Moral Theory Be? (ch. 7-8) – Philosophy.Uncc.edu.

External links
Mor – Wiktionary.

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