In the first month, the month Nisan. See the comment on Nehemiah 2:1. This name was first given to the month by the Jews after the return from the captivity. It was the Babylonian name of the first month of the year, and superseded the old Jewish name, Abib.
The twelfth year of … Ahasuerus—b.c. 474, if Ahasuerus be Xerxes. They cast Pur, that is, the lot. The superstitious use of lots has always been prevalent in the East, and continues to the present day.
Lots were drawn, or thrown, m various ways: sometimes by means of dice, sometimes by slips of wood, or strips of parchment or paper, and also in other manners. Even the Jews supposed a special Providence to preside over the casting of lots (Proverbs 16:33), and thought that matters decided in this way were decided by God.
Haman appears to have cast lots, first, as to the day of the month which he should fix for the massacre, and secondly as to the month in which it should take place. Apparently the lot fell out for the thirteenth day (Nehemiah 2:13), and for the twelfth month, the last month in the year.
The word "Pur" is not Hebrew it is supposed to be Old Persian, and to be connected with Mod. Pers. pareh, Lat. pars, Greek μέρος μοῖρα. To the twelfth month, that is, the month Adar. Adar is, like Nisan, a Babylonian word, perhaps connected with edder, "splendour."
The month so named corresponded nearly with March, when the sun begins to have great power in Western Asia.