I am interested in conditions under which a community adopts (or does not adopt) another language, even though this community is sufficiently isolated to be able to continue the use of its previous language. There are two examples that I have in mind:
- Yiddish is a Germanic language adopted by European Jews, even though being a religiously closed community they didn't necessarily need to adopt it for their internal communication, as they did not adopt later Polish, Russian, or Lithuanian, despite living for centuries in the lands where these langauges are spoken. However, I guess a possible answer to this question may be that in the period of adopting Yiddish the Jewish community was not as isolated as in later centuries (when it was essentially forced to live in Ghettos).
- French as the language of Russian aristocracy I posed this question in the French forum, but did not receive answers based on any real data. Therefore, my grounds for believing that it was adopted as a mother tongue by the majority of the Russian aristocracy are anecdotal (based on reading Pushkin and Tolstoy). Still, assuming that this was the case: how could a foreign language penetrate so deeply into a society geographically and politically isolated from France, and why French and, e.g., not German (which seems to me a more natural choice, given Russia's political ties to Germany and Austria and the fact that it was the native language of many of the Russian rulers in the preceding century)?
Other examples are welcome as well.