Rashi does bring Arabic words, as well as German, Slavic and Russian.
Although finding a similar word in a different language is a good backup, it is not the be-all-end-all. Rashi gave a word because of what he was Mekabel or built from Raayos, not in a vacuum. Perhaps you can say that had he known of two languages with similar words that would have swayed his reasonning to translate it as such, but that’s it.
It is very likely that Rashi’s unclear
description may have come from the
simple fact that rice cultivation wasn’t
introduced into France until over 300
years after Rashi was nifter
Problem with that is that tosafos does say it means rice. Tosafos is not 300 years later.