A Torah source is often referred to as a M"M, which I have heard read as both מורה מקום, Moreh Makom and מראה מקום, Mar'eh Makom, (see here for example) which have similar meanings, and mean something like "placefinder".
On the one hand, the Talmud uses Mar'eh Makom in a number of places to refer to a placeholder (e.g. Bava Basra 76b, Kiddushin 48b). On the other hand, in the introduction to the Beis Yosef, Rav Yosef Kar'o uses the word Moreh Makom to mean finding a source for a Halacha.
Which is technically more correct/older when referring to a Torah source, and are there any articles that discuss this and conclude one way or the other?