The term "supernatural" comes from the term "supernauturalator" or "Supernature." Dionysius the Areopagite (around 500AD) began talking of God as the supernaturalator, meaning that God's higher nature was the telos toward which our "lower" natures were drawn. St.Augustine has spoken of Divine nature as "Supernature" or the higher form of nature, but that is speaking of nature in you, like human nature and divine nature.
In the beginning the issue was not a place, "the realm of the supernatural '' but the issue was the nature inside a man. Human nature, vs. divine nature. The Supernatural was divine nature that drew the human up to itself and vivified it with the power (dunimos) to live a holy life. This is the sort of thing Paul was talking about when he said "when I am weak I am strong." Or "we have this treasure in earthen vessels." The weak human nature which can't resist sin is transformed by the power of the Godly nature, through the spirit and becomes strong enough to resist sin, to be self sacrificing, to die for others ect ect.
This was the "supernatural" prior to the reformation. It was tied in with the sacraments and the mass. That's partly why the Protestants would rebel against it. Austine (late 300s early 400s) spoke of Christians not hating rocks and trees, in answer to the assertion that Christians didn't like nature. But the extension of the natural world as "nature" didn't come until later. The idea of "the natural" was at first based upon the idea of human nature, of biological life, life form life, that's what the Latin natura is about.
Prior to the reformation Christian theologians did not see the supernatural as a separate reality, an invisible realm, or a place where God dwells that we can't see. After the reformation reality was bifurcated. Now there came to be two realms, and they juxtaposed to each other. The realm of Supernature, is correlated to that of Grace, and is holy and sacred, but the early realm is "natural" and bad it's mired in sin and natural urges.
But all of that represents a degraded form of thinking after going through the mill of the Protestant Catholic split. The basic split is characterized by rationalism vs fideism. The Catholics are rationalists, because they believe God is motivated by divine purpose and wisdom, the Protestants were fideists, meaning that faith alone apart form reason because God is motivated by will and sheer acceptation, the desire to prove sovereignty above all else.
The rationalistic view offered a single harmony, a harmonious reality, governed by God's reasoned nature and orchestrated in a multifarious ways. This single reality continued a two sided nature, or a multi-facets, but it was one harmonious reality in which human nature was regenerated through divine nature. But the Protestant view left Christian theology with two waring reality, that which is removed from our empirical knowledge and that in which we live.
The true Christian view of the Supernatural doesn't see the two realms as juxtaposed but as one reality in which the natural moves toward its' ground and ends in divine nature. It is this tendency to move toward the ground and end, that produces miracles. A miracle is merely nature bending toward the higher aspect of Supernature.
But with the Protestant division between divine sovereignty, acceptation and will motivating the universe, we mistake univocity and equivvocity for nature and supernature. We think nature and supernature are not alike, they are at war, so difference marks the relationship of the two. But to make the Supernatural more available they stress some aspect of nature and put it over against the rest of nature and pretend that makes it supernatural, this is univocity, it's the same. So will and acceptation, sovereignty, God has to prove that he is in charge, these are all aspects of univocity.
It's the natural extension of this bifurcation that sets up two realms and sees nature as "everything that exists." or "all of material reality" that sets up the atheist idea that supernatural is unnecessary and doesn't exist.