The interpretation timeline
1 Samuel 9:9 Douay-Rheims

Now in time past, in Israel when a man went to consult God he spoke thus: Come, let us go to the seer. For he that is now called a prophet, in time past was called a seer.

A.D. 235 – 1871 7 witnesses

Patristic

before A.D. 750
235
A.D.
Hippolytus of Rome Patristic
c. A.D. 170–235
“For with what reason should the prophet be called a prophet, unless he in spirit foresaw the future? For if the prophet spoke of any chance event, he would not be a prophet then in speaking of things which were under the eye of all. But one who sets forth in detail things yet to be, was rightly judged a prophet. Wherefore prophets were with good reason called from the very first "seers."”
Source
430
A.D.
Augustine of Hippo Patristic
A.D. 354–430
“I wonder how that opinion could have arisen whereby sight is thought to belong to bodies only. But, from whatever habit of speech that opinion may have come, the holy Scriptures are not accustomed to speak thus; they attribute vision not only to the body but also to the spirit, and more to the spirit than to the body. Otherwise they would not have been right in giving the name seers to the prophets who saw the future not by bodily but by spiritual sight.”
Source

Scholastic

c. 1100 – 1500
1105
A.D.
Rashi Jewish
1040–1105
“In former times in Yisroel. The author wrote this verse, i.e., this is not part of the youth of Shaul's statement. For the "prophet" of today. The one who is called 'prophet' today was formerly called 'seer.'”

Post-Reformation

c. 1650 – 1900
1771
A.D.
John Gill Reformed
1697–1771
“Before time in Israel, when a man went to inquire of God,.... To ask doctrine of him, as the Targum, to be taught by him, to have his mind and will in any affair of moment and importance; which was usually done by applying to some man of God, eminent for grace and piety, and a spirit of prophecy: thus he spake, come, and let us go to the seer; a man used to say to his friend, when he wanted some instruction or direction, let us go together to such an one, the seer, and ask counsel of him what is proper to be done in such an affair: for he that is now called a prophet was before called a seer; for though these names are used freely of the same persons, both before and after this time; yet now the more common appellation which obtained was that of a prophet; custom, and the use of language, varied at different times, though the same was meant by the one and the other; such men were called seers, because of the vision of prophecy, because they saw or foresaw things to come; and they were called prophets, because they foretold what they saw, or delivered out their predictions by word of mouth. This verse is put in a parenthesis, and is commonly supposed to be the words of the writer of this book: hence some draw an argument against Samuel being the writer of it, as Abarbinel does, who concludes from hence that it was written by Jeremiah, or some other person long after Samuel, or that this verse was added by Ezra; but as this book might be written by Samuel in the latter part of his life, he might with propriety observe this, that in his younger time, and quite down to the anointing of Saul king, both when there was no open vision, and afterwards when there was scarce any that had it but himself, he was used to be called the seer; but in his latter days, when there were many that had the vision of prophecy, and there were schools set up, it was more common to call them prophets; though perhaps these are the words of Saul's servant, spoken to encourage Saul to go to the man of God, and inquire of him, since in former times, as he could remember, being perhaps an old servant, or he had heard his parents so say, that such men used to be called seers, because they saw what others did not, and declared and made others to see what they did; and therefore there was a probability that this man of God, who was a seer, might show them the way they should go to find the asses.”
Source
1832
A.D.
Adam Clarke Methodist
1762–1832
“Beforetime in Israel - This passage could not have been a part of this book originally: but we have already conjectured that Samuel, or some contemporary author, wrote the memoranda, out of which a later author compiled this book. This hypothesis, sufficiently reasonable in itself, solves all difficulties of this kind. Was beforetime called a seer - The word seer, ראה roeh, occurs for the first time in this place; it literally signifies a person who Sees; particularly preternatural sights. A seer and a prophet were the same in most cases; only with this difference, the seer was always a prophet, but the prophet was not always a seer. A seer seems to imply one who frequently met with, and saw, some symbolical representation of God. The term prophet was used a long time before this; Abraham is called a prophet, Gen 20:7, and the term frequently occurs in the law. Besides, the word seer does not occur before this time; but often occurs afterwards down through the prophets, for more than three hundred years. See Amo 7:12; Mic 3:7. All prophets, false and true, profess to see God; see the case of Balaam, Num 24:4, Num 24:16, and Jer 14:14. All diviners, in their enthusiastic flights, boasted that they had those things exhibited to their sight which should come to pass. There is a remarkable account in Virgil which may serve as a specimen of the whole; the Sibyl professes to be a seer: - - Bella, horrida bella, Et Tyberim molto spumantem sanguine Cerno. Aen. lib. vi., ver. 86. Wars, horrid wars, I View; a field of blood; And Tyber rolling with a purple flood. I think the 9th verse comes more naturally in after the 11th.”
Source
1849
A.D.
1774–1849
“A seer. Because of his seeing, by divine light, hidden things, and things to come, (Challoner) by inspiration. (Worthington) — They had the things which they foretold so clearly in view. The Sybil cries out, Bella, horrida bella. Et Tiberim multo spumantem sanguine cerno. (Virgil)”
1871
A.D.
1871
“seer . . . Prophet--The recognized distinction in latter times was, that a seer was one who was favored with visions of God--a view of things invisible to mortal sight; and a prophet foretold future events.”
Modern · 1953 →

The in-app commentary runs from the Fathers to the early-modern record, then stops — that's where the public-domain sources end, not where the reading does. For the modern reading, follow the sources directly.