5 This much, then, on the preliminary circumstances, by occasion of which He came to a conversation with that woman, let us look at the matters that remain; matters full of mysteries and pregnant with sacraments. “And He must needs pass through Samaria. He comes then to a city of Samaria which is called Sychar, near to the parcel of ground which Jacob gave to his son Joseph. Now Jacob's fountain was there.” It was a well; but every well is a fountain, yet not every fountain a well. For where the water flows from the earth, and offers itself for use to them that draw it, it is called a fountain; but if accessible, and on the surface, it is called only a fountain: if, however, it be deep and far down, it is called a well, but in such wise as not to lose the name of fountain.
Source: Tractates on the Gospel of John (New Advent)