This article (Shook, 2015) makes a distinction between "ethical naturalism" and "moral naturalism":
Moral naturalism as defined at the conclusion of the previous section is distinct from both ethical naturalism and moral realism. Ethics is the philosophical domain that deals with meta‐level issues about ways for determining the meanings and applicability of moral norms and terms, questions about the appropriate methods for judging and answering moral problems, and concerns over whether better moralities, or even one correct morality, can be determined. Ethical naturalism therefore goes much further than moral naturalism, by not only agreeing that actual morality should be studied naturalistically, but additionally claiming that all those meta‐level issues are questions to be answered by empirical sciences as well. If successful, ethical naturalism would render moral nihilism, scepticism, subjectivism, and relativism all obsolete.
But according to Wikipedia, "ethical naturalism" and "moral naturalism" are synonymous:
Ethical naturalism (also called moral naturalism or naturalistic cognitivistic definism)1 is the meta-ethical view which claims that:
The SEP only wrote about "moral naturalism" (in this article, the term "ethical naturalism" appears only once).
Britannica only wrote about "ethical naturalism" (in this article, the term "moral naturalism" doesn't appear).
So I don't know if the SEP article, the Britannica article, and the Wikipedia article are talking about the same thing.
I also read on this website that ethics and moral philosophy are equivalent terms.
Shook, J. R. (2015). Humanism, Moral Relativism, and Ethical Objectivity. The Wiley Blackwell Handbook of Humanism, 403-425.