According to Plaut ("The Torah a Modern Commentary", Revised Edition, p. 530) the term "ger" has changed over time.
Ger was the term applied to resident non-Israelites who could no longer count on the protection of their erstwhile tribe or society.(9)
- Later Jewish tradition distinguished between the ger toshav, the resident stranger, i.e., a non-Jewish resident (of the land of Israel) who observed the seven Noahide laws, and the ger tzedek who had become a full proselyte.
I read this to mean that originally the term "ger" was applied to the resident non-Israelite, but later the term "ger" was refined by using either ger toshav or ger tzedek in order to be more descriptive of the stranger being discussed.
When did this change in usage occur? Deuteronomy, post-Torah, earlier, later?
I have seen this earlier question, Ger Tzedek/Tzadik earliest sources and definition, but it does not answer my question.