Origin of the Popular Distinction Between Morals and Ethics

Short answer

In common English language, there is no difference. It is just Greek vs. Latin roots for words meaning the same. Your findings also do not concur with anything I know from philosophy (see this answer of mine for context, reference, and etymology).

In philosophy, though, there is one philosopher in particular who famously made a difference between ethics and morals: Immanuel Kant. That it is Kant who did this is not a fluke, but due to the German use of the words at the time. Here, Ethics is about everything freedom or about empirical rules for wellbeing, while Morals is about the rational analysis of the laws of freedom.

Long answer

All quotations from: Immanuel Kant, Groundwork of the Metaphysics of Morals: A German-English Edition, Mary Gregor and Jens Timmermann (eds., trs.), Cambridge University Press, 2011

All rational cognition is either material and considers some object, or formal and occupied merely with the form of the understanding and of reason itself, and with the universal rules of thinking as such, regardless of differences among its objects. Formal philosophy is called LOGIC, whereas material philosophy, which has to do with determinate objects and the laws to which they are subject, is once again twofold. For these laws are either laws of nature, or of freedom. The science of the first is called PHYSICS, that of the other is ETHICS; the former is also called doctrine of nature, the latter doctrine of morals. (AA: IV 387)

Here, it seems like there was no difference, since the science of the laws of freedom is called ethics OR doctrine of morals. That is not the whole story, though:

In this way there arises the idea of a twofold metaphysics, a metaphysics of nature and a metaphysics of morals [Metaphysik der Sitten]. Physics will thus have its empirical, but also a rational part; so too will ethics, though here the empirical part might in particular be called practical anthropology, the rational part actually moral science [Moral]. (AA: IV 388)

Here, at least in the German original, there is a difference: while ethics are all systemic endeavours regarding the laws of freedom, morals proper are strictly about the rational and, in turn, not about the empirical part.

The commentary explains where this is coming from, explaining why Timmermann differs here from the classic Gregor translation:

IV388.13 Moral] 'moral science'. For want of a better word, one archaism replaces another to English a third. In the eighteenth century, Moral was used for the systematic study of morality, but not for morality itself (Sittlichkeit, Moralität). Like most translators, Gregor uses 'morals' for Moral, but also - as in the title of the book - for Sitten (people's mores), i.e. there is no way of telling from her translation whether Kant is speaking about the principle of moral conduct or of moral thought (see for instance IV440.30). Neither 'ethics' nor 'moral philosophy' is available to translate Moral because they are used for Ethik and Moralphilosophie respectively, and Moral is a somewhat broader notion than either. 'Moral science' is the only feasible option. (pp. 161-62)

Thus, the reason why Kant can make this difference is that in German, there already was a difference in the use of the words.

I also am pretty certain Kant wrote somewhere that another valid use of "ethics" is about "that which is good for me", ie. that which works towards my individual wellbeing, although I cannot find the source at the moment.

The only real difference between morals and ethics is that the term 'morals' has a decidedly Christian religious connotation. I mean, according to my dictionary etymologically the term 'morals' is derived from a 6th century book by Saint Gregory the Great titled "Moralia", which was an exposition on the Book of Job. The terms 'ethics', by contrast, comes from the pre-Christian Greek philosophical phrase "hē ēthikē tekhnē", which means (roughly) 'the science of character'. 'Morals' tends to sound a bit more 'preachy' for that reason.

Which term you should use is mostly a matter of what audience you're speaking to and what subject you're speaking on. If you're dealing with a Christian audience or topic, 'morals' is more appropriate. Secular academic philosophy tends to prefer the term 'ethics', both for its Aristotelean roots and its more neutral tone. Regular people generally don't think too much about the distinction and are usually more habituated to the term 'morals', but in some cases they may find that term politically offensive. You pays your money and you takes your chances…

In this context, the distinction appears to be an opinionated one: it concerns the "ethical" obligation that one has to follow professional regulations whether or not they conform to personal "morality".

The word "morality" and "ethics" and the adjectives "moral" and "ethical" can be used interchangeably, and are often used interchangeably (also outside philosophical discourse).

There seems to be some linguistic drift going on however. If you look at the Google Ngram viewer for the entry "ethics, morality", then it is very remarkable that

• Around 1800, "morality" was much more frequent
• From 1800 to 1920 the words drifted closer together
• From 1920 to 1980 they had approx. the same frequency
• Since 1980 they started to drift apart, so that currently "ethics" is significantly more frequent

This also happens to very roughly correlate with a frequency drift of the words "individual" and "social". Those two words started to drift apart since about 1940, so that currently "social" is much more frequent. Now, when you look at the bigram frequencies it also appears that "ethics" is more closely associated with "social", whereas "morals" is more closely associated with "individual". Since about 1900 the bigram "social ethics" starts to become much more frequent than "social morality". However, the bigrams "individual ethics" and "individual morality" show rougly the same frequencies.

So, to make the observation more precise: Rougly since 1980 the word "ethics" becomes much more frequent than "morality". There also appears to be a somewhat longer linguistic trend that associates "ethics" more closely with "social" and "morality" more with "individual".

One cause of this, surely, must be the rise of applied ethics in the form of explicit "business ethics", bioethics, medical ethics, computer ethics, and the like. All of those only started to take off roughly since the 1980's. Another cause could also be increased secularisation (since "morality" is associated more with religion and the focus in religious education or proselitizing is usually on invividual morality).

Wittgenstein famously advised us to "don’t think, but look!" (PI 66). That is, don't invent etymological rationalizations or "just-so" stories about the meaning of words and about how those meanings came about, but consider the actual data and see how words diffused in actual usage. The Ngram viewer and large text corpora now give us the tools to look at raw linguistic data (which then, of course, still need to be correlated with their social sources and contexts). To explore the difference between "ethics" and "moral" it's also pretty remarkable to see the development of the bigrams "ethical policy, moral policy" (again divergenging sharply since the 1980's) and compare this to "ethical values, moral values". Or look at "unethical versus immoral".

To summarize (=rationalize) the difference I would say that - since about the 1970's, 1980's, due to the rise of so-called applied ethics, "ethical"/"unethical" has come to more closely connotate the ethics of a particular social role (especially of professional roles), while "moral"/"immoral" stayed closer to its existing meanings, connotating the ethics of a person seen as individual person. (In both cases we're talking about moral/ethical norms and values, however.)

See the Daimonion of Socrates (Wikipedia link). This is a first clear articulation of conscience, seperate from game-theory self-interest, or holding to divine laws. Biologically, I would describe conscience as exactly that, the experience of collective benefits of certain behaviours and values, as more important than personal benefit of eschewing them. That is, our eusociality, our ability to cooperate, feeling more valuable than self-interest.

I argue here that Socrates is paradigmatic in defining philosophy from other wisdom traditions: Weren't there any philosophers from Africa, America or the Middle East before Socrates? His 'martyrdom' for wisdom, his choice to give up his life and drink hemlock rather than recant his views which he described his conscience or daimonion as dictating, had a profound influence on Western thought exactly because he was saying, this behaviour of Socratic dialogue, and the challenge to 'piety' of the Euthyphro Dilemma, which I'd say is the core of what got him a death sentence, that these were values that could enable something about a collective holding to them, worth giving up his life for.

Plato took Socratic dialogue and the math-mysticism of Pythagoras to create his Academy, and so academia. Aristotle's Lyceum modelled the aspiration to universal education, and so universities. In this conscience, and a mutual interest in finding the truth, wins above rhetoric and sophism, over formal debate based on winning over an audience. Science requires a personal adherence to it's standards, not simply a wish for prestige by any means. We see this manifested in how scandalous scientific fraud is, to distort results like data dredging eg p-hacking, can disqualify someone from any credibility in their scientific work.

So, I would describe this as an articulation of morality, of the personal experience of the moral weight of actions, of when collective benefits are felt to outweigh any personal gain. This is key to any military, a soldier must be willing to die for their polity, and that is a core feeling, that defending a collective is worth sacrificing the personal, which enables civilisation, cities and polities. See Hume's "Reason is, and ought only to be the slave of the passions, and can never pretend to any other office than to serve and obey them", which highlights that felt motivations are fundamental, and reasoning can only come after.

Ethics however is not about the personal feelings, the inner conscience, but about persuading others how they should behave. This I argue fundamentally depends on intersubjective reasoning, here: Is the Categorical Imperative Simply Bad Math? :) That is, ethics must appeal to or educate the conscience.

Moral Foundations theory (Wikipedia link) is based on research showing there are core cultural universals, that seem to have evolved to support prosocial behaviour, eg a drive for fairness/justice. We can see this iterating from Ancient Greek myths about how bad absolute rulers eg Sisyphus, Minos, and Midus, could in some sense escape accountability in their lifetimes, but not beyond that; up to the Abrahamic idea that im this life, no one is above the law, which has enabled larger scale cooperation (at least, for now..).

There seem then to be core drives which evolved to let us cooperate, which we relate to conscience, morality, and the felt moral weight of actions. Then there is ethics, which aims to appeal to educate and refine the consistency of how we act on our moral feelings.

There is a failed assumption to intersubjectivity. There is a low but stable number of sociopaths and psychopaths across all societies. The gains from collective cooperation, are always being tested by people who simply do not feel the intrusion of conscience that most people feel. Machiavelli is the philosopher who spoke to this kind of realpolitik most clearly. I would argue game-theory is even more fundamental than conscience and morality. However virtuous and noble, genes that don't replicate leave the genepool. Ethical reasoning seeks to persuade others to hold to unstable equilibria for collective benefit, to take the Prisoner's Dilemma choice of net benefit. That is the reasoning idealistic mode, persuading others to be good serves our mutual interests. But we all know an unreasoned selfishness is there too, testing whether the sacrifices we make to collaborate are truly worthwhile. Socrates had a conscience that overpowered his survival instinct, easily heroised, harder to live. This is the tension between idealistic universalising ethics, and felt morality where we wish to be heroes -even martyrs- but mostly, are not.

I believe the pragmatic distinction arose because of the different contexts in which the words are typically used. Preachers and prohibitionists preferred "moral" so lawyers and academics started preferring "ethical" to distinguish themselves from the riffraff. It became something of a class distinguisher, and from there the class that used "ethical" started injecting their prejudice that that their sense of ethics was higher and better than that of the hoi polloi back into the preferred terms

Morals are the guidelines for conduct and ethics is the study of the system that generates these guidelines. So there could be a system of morality, like Jainism, that prescribes ahimsa (nonviolence) and ethics investigates how Jainism justifies it, why should we be nonviolent?