What is the difference between Morals and Ethics?

And where does the difference come from?

Wikipedia says:

Aristotle first used the term ethics to name a field of study developed by his predecessors Socrates and Plato. In philosophy, ethics is the attempt to offer a rational response to the question of how humans should best live.

This makes sense but is not very complete. I found the Encylopedia Britannica was better:

Many people think of morality as something personal and normative, whereas ethics is the standards of "good and bad" distinguished by a certain community or social setting.

The article (the whole thing is worth reading) finishes with this admonishment:

Ethicists today, however, use the terms interchangeably. If they do want to differentiate morality from ethics, the onus is on the ethicist to state the definitions of both terms.

Another common summary of the difference I found is that morals about personal beliefs and ethics are about how to act in a community (which could be the whole world).

I wrote about this in a completely different context (open source) a few years ago.

But today, I came across this quote from Henry Sidgwick in “The Methods of Ethics” (Chapter 14: Ultimate Good)

At the outset of this treatise I noticed that there are two forms in which the object of ethical inquiry is considered; it is sometimes regarded as a Rule or Rules of Conduct, ‘the Right,’ sometimes as an end or ends, ‘the Good.’ I pointed out that in the moral consciousness of modern Europe the two notions are prima facie distinct; since while it is commonly thought that the obligation to obey moral rules is absolute, it is not commonly held that the whole Good of man lies in such obedience; this view, we may say, is—vaguely and respectfully but unmistakably—repudiated as a Stoical paradox. The ultimate Good or Wellbeing of man is rather regarded as an ulterior result, the connexion of which with his Right Conduct is indeed commonly held to be certain, but is frequently conceived as supernatural, and so beyond the range of independent ethical speculation.

The first sentence is pretty close to the common differentiation between moral beliefs and ethical behavior. But Sidgwick makes the very interesting (to me) point that this split is rooted in European religious belief (I assume he means Christianity, though he references the Stoics).

Writing it down as something to watch for in further readings.

PS — “The Methods of Ethics” is an incredibly dense but rewarding read. I understand why David Parfit and others think it is so good.