Cheshvan is the eighth month of the Jewish calendar counting from Nisan. Throughout the Mishnah and Talmud, and many later works, the month is called Marcheshvan.
Some explain that the word “mar” means “bitterness”, while others maintain that it means “a drop of water,” as in the verse “like a drop (mar) from a bucket” (Yeshayahu 40:15). It is in this month that Jews in the land of Israel begin praying for rain. Additionally, the Mabul (Great Flood) in the times of Noah began (and ended) in this month.
In the Book of “Melakhim” (“Kings”) Cheshvan is called “the month of Bul”, as in this verse, describing the building of the Jerusalem Temple in the times of King Shlomo:
“and in the eleventh year, in the month of Bul—that is, the eighth month—the House was completed according to all its details and all its specifications. It took him seven years to build it” (Melakhim Alef, 6:38).
“In the month of Bul”. This is [the month of] Mar Cheshvan; [when] the grass in the field decays, and cattle is given fodder from what is stored, from the expression “and he gave fodder [ויבל] to the donkeys” (“Shoftim”, 19-21).
Unlike the month of Tishrei, which is full of holidays and spiritual experiences, Cheshvan is a month of mundane activity. It is actually the only month in the Hebrew calendar that does not have any holidays or special mitzvot at all!
However, there is an opinion that they should appear in the future. The Chassidic Masters say, that the month of Cheshvan is especially “reserved” for the time of Moshiach, who will choose this month to inaugurate the Third (and Eternal) Beit haMikdash in Jerusalem.