Etymology: The root of the words 'real' and 'reality'

The best treatment I know of is by Raymond Williams as part of his entry on “Realism” in Keywords: A Vocabulary of Culture and Society (page 259), which I have excerpted below.

It is from [old French] real, [to the late Latin] realis, from [the ultimate traceable (Latin) word] res — thing. Its earliest English uses, from C15, were in matters of law and property, to denote something actually existing. There was a connected and persisting later use for immovable property, as still in real estate. The sense of something actually existing was transferred to general use, from lC16, in an implicit or explicit contrast with something imaginary: ‘Is’t reall that I see?’ (All’s Well That Ends Well, V, iii); ‘not Imaginary, but Reall’ (Hobbes, Leviathan, III, xxxiv). But at the same time there was an important sense of real as contrasted not with imaginary but with apparent: not only in theological arguments about the ‘reall presence’ of Christ in the materials of communion, but also in wider arguments about the true or fundamental quality of some thing or situation — the real thing, the reality of something. This use is still very common, if often not noticed as such, in phrases like ‘refusing to face the real facts of his situation’ or ‘refusing to face reality’. Since the use to indicate something tangible, palpable or factual was also strongly continued, it can be seen that there is almost endless play in the word.