Esther 9:26 (ESV)

26 Therefore they called these days Purim, after the term Pur. Therefore, because of all that was written in this letter, and of what they had faced in this matter, and of what had happened to them,

The word purim is the plural form of the Akkadian word “puru,” which means lot. One could loosely translate purim as turn of fate. This is an ironic name that demonstrates that the fate of the Jews had never been in the hands of Haman and his astrologers. No, God had determined the events that took place on the thirteenth of Adar.

This verse gives two reasons why the Jews henceforth celebrated the Purim feast. The first is out of respectful obedience to Mordecai, who had ordered the feast in his letter. The second reason is that they themselves felt compelled to remember and celebrate the marvellous events by which they were rescued.