Q. Why is there some reluctance to the use of the names of the secular months in our days, while we accepted totally the use of Aramaic names of months, such as Tishrei, Cheshvan etc.? Why not keep the Torah names for the months, such as Chodesh Harishon, Sheni. etc.?
A. The most prominent and accepted answer is given by the Ramban (Shemos 12: 2), who explains that the names of the months came with us from Babel (Talmud Yerushalmi- Rosh Hashanah 6a). The reason for this is that in the beginning when the Torah was given, the order of the months was as a remembrance of the Exodus from Egypt, but when we left Babel and the posuk (Yirmeyahu 16: 14-15), was fulfilled: “That it shall no more be said: Chai Hashem, Who brought up the Bnei Yisrael from the land of Mitzrayim, rather Chai Hashem, who brought up the seed of the House of Yisrael from the land of the north. Therefore, we returned to calling the months by the names by which they were called in Babylonia, as a reminder that there we stood and from there Hashem drew us out. For the names Nisan, Iyar, and the others are Persian names and are only found in the books of the Babylonian prophets (Zechariah 1: 7, Ezra 6: 15, Nehemiah 1: 1) and in Megilas Esther (3: 7). Therefore the verse says, “In the first month, which is the month Nisan,” similar to, “They cast pur, that is, the lot” (ibid.). And until today the nations in the lands of Persia and Media call [the months] Nisan and Tishrei and all the rest like us. And these [names] recall through the months the second redemption just as we did until now for the first one.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a