The concept of religion was derived from the Latin term religio, which roughly corresponds to the words “scrupulousness,” “conscientiousness,” “devotedness,” or “felt obligation.” The word was associated to practices that were not necessarily related to gods. As a noun it was used to refer to “worship.” As an adjective, it referred to “people who were devout.”
Schilbrack, K. (2022). The Concept of Religion. In E. N. Zalta (Ed.), The Stanford Encyclopedia of Philosophy (Summer 2022). Metaphysics Research Lab, Stanford University. https://plato.stanford.edu/archives/sum2022/entries/concept-religion/
The concept religion did not originally refer to a social genus or cultural type. It was adapted from the Latin term religio, a term roughly equivalent to “scrupulousness”. Religio also approximates “conscientiousness”, “devotedness”, or “felt obligation”, since religio was an effect of taboos, promises, curses, or transgressions, even when these were unrelated to the gods.
The concept religion did not originally refer to a social genus, however. Its earliest references were not to social kinds
the term continued to be used, as it had been in antiquity, in adjective form to describe those who were devout and in noun form to refer to worship