Q. Certain months appear in the Torah, e.g. Aviv, the month of spring. Others are identified by numbers, e.g. “The 7th month” (=Tishri). What about the current names?
A. Some come in the later books of Scripture; most are post-exilic and are from other languages.
• Nisan is linked with the Babylonian first month, Nisanu; some derive it from the Hebrew n-s-a, to start. In the Torah it is Aviv, spring.
• Iyyar may be associated with the Hebrew or, light. In Tanach it is Ziv, brightness.
• Sivan is possibly linked with Assyrian Samu/Asamu, to mark or appoint, like sim in Hebrew.
• Tammuz may be from “Dumuzi”, a semitic deity.
• Av is an Assyrian name not mentioned in the Bible. A fuller version, M’nachem Av, “Av the Comforter”, recalls the belief that the Messiah will be born in this month.
• Ellul is Babylonian (Neh. 6:15).
• Tishri is from sherai/shera, to begin.
• Cheshvan or Mar-Cheshvan (I Kings 6:38) may be from the Assyrian Arahsammus, eighth month.
• Kislev is Assyrian (Zech. 1:1, 7:1).
• Tevet (Esther 2:16), linked with the Assyrian/Babylonian Tebetum, may be from a Hebrew root taba, to dip or sink (there is much rainfall this month).
• Sh’vat (Zech. 1:7) could be from a root sh-t, beating or shrinking.
• Adar (Esther 3:7) is possibly from “Adromelech”, a son of the king (Sennacherib).