Month of flowers, (Neh. 2:1) the first month of the Jewish sacred year. (See ABIB.) Assyrian nisannu, “beginning.”
International Standard Bible Encyclopedia 1915
ni'-san (nican): The first month of the Jewish year in which occurred the Passover and which corresponds to April. The month is the same as Abib, which occurs in the Pentateuch. Nisan occurs in Ne 2:1 and Es 3:7. It denotes "the month of flowers."