In this answer to a question that concerned the ways in which languages change and evolve, @SethJ made reference to a sugya that discusses the differences between different dialects of Aramaic, and a corresponding Tosafot that evidences an awareness of different Romance languages belonging to the same language family. I am trying to find this sugya (and this Tosafot), but with no avail. Does anybody know which passage SethJ was referring to?
(I have already asked this by means of a comment on SethJ's answer, but since he doesn't know I figure that asking it again as its own question might draw it to the attention of a broader range of people.)