As I previously said in one of these topics, the uvular "r" in French is a recent evolution of the prononciation, it dates backs in the 2 lasts centuries. So it is clearly not of celtic or Germanic origins.
This prononciation has known a wide spread in the 19th and 20th centuries; When France had recieved a lot of imigration from Italy, Spain, Portugal and central Europe. If it has a foreign origin we would have more chance to find it there.
Anyway, the prononciation of these sounds "r", rolled or uvular doesn't have any importance. One can speak French with rolled "r", it still be french. even nowaday you can find native french speakers who roll the "r".
The same way for the "nasal" sounds likes "en", "in", "on", etc. It is not necessary to prononce them "nalized". A lot of regional accents doesn't.
This prononciation has known a wide spread in the 19th and 20th centuries; When France had recieved a lot of imigration from Italy, Spain, Portugal and central Europe. If it has a foreign origin we would have more chance to find it there.
Anyway, the prononciation of these sounds "r", rolled or uvular doesn't have any importance. One can speak French with rolled "r", it still be french. even nowaday you can find native french speakers who roll the "r".
The same way for the "nasal" sounds likes "en", "in", "on", etc. It is not necessary to prononce them "nalized". A lot of regional accents doesn't.