Parshas Hachodesh Part 1: Jewish Months?

Shiur from Rabbi Elimelech Kohn Ztl on פרשת החודש.Discussed: The Ramban explains when and why we started calling the months by name (Nissan Iyar etc); names that are not Jewish but rather based on Persian/Babylonian pagan God's. This leads to the question, why are we using Persian names for our calendar? The Sefer Haikram asks, how could the Jews adopt non-Jewish Persian names of the months? Doesn't the Torah command us to count the months by number starting from Nissan? The Sefer Haikram concludes that this demonstrates that parts of the Torah can change, arguing against the Rambam's Ninth Principle, that the Torah is immutable and will never change.