Without knowing anything about sacred books and the like, one can see that the point that matters here is that at this or that point in time, a word that is translated, for lack of anything more precise, as “nation” has come to mean “born outside the tribe / not of Jewish ancestry” in the general language, Jewish and non.
I understood the point, but I don’t think it’s correct. Look at the first verse of the second Psalm. You see a usage of “goyim” that roughly means non-Jews because it refers to the nations of the world. Goy as just nation and as non-Jew are related meanings, or shadings, and you already see it in the Torah (or Bible if you like.) I don’t think the Torah uses the singular “goy” to mean an individual non-Jew, but the meaning of nation never went away. You have to imagine a whole literacy based on Jewish texts. Quote “nation will not lift up the sword against nation anymore” in Hebrew to a Jewishly literate person and he might be reminded of the familiar song “Lo yisa goy el goy cherev….”