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)
> 
> 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][1], but it does not answer my question.


  [1]: https://judaism.stackexchange.com/questions/68286/ger-tzedek-tzadik-earliest-sources-and-definition