My friend told me how the word das, which we use to mean halacha or religion, like k'das Moshe veYisroel, is actually a Persian word. If this is true, then how can commentators explain the word aishdas in Vezos haBracha as meaning a fiery law, if Persia and Persian did not exist at the time of the Torah? The same question goes for any similar instance in Tanach, if there are any.
Here are some sources about das being of Persian origin. Perhaps there are some more reliable sources too.