For this did they call these days "Purim," after the pur... (Esther 9:26)It's worthwhile to consider why Purim is called Purim; all of the other holidays are named for their associated miracle. Pesach is named after the event in which God passed over the houses of the B'nei Yisrael, Shavuot due to the revelation at Sinai, etc. Why then is Purim named after the dreaded plot that the wicked Haman attempted to carry out?
The AR"I HaKadosh writes that the months of the Jewish calendar correspond to different parts of the human head. The month of Tishrei is the cranium, Cheshvan and Kislev are the two ears, and Tevet and Shevat are the two eyes.
The month of Adar corresponds to the nose, the appendage that is associated with the sense of smell.
As we mentioned earlier, all of the senses were implicated in the original sin of Adam, and consequently blemished by that sin. The only exception was the nose, which is why until this day the sense of smell is entirely spiritual (i.e. the soul and not the body derives benefit from it), and in fact will be the means for Moshiach to root out the evil from the righteous.
Now, we know that Haman the descendant of the wicked Agag of Amalek drew his strength from the primordial serpent who enticed Adam and Eve to sin by eating and enjoying the fruit of the Tree of Knowledge. In fact, we see that Haman himself sought to cause the Jews to sin in a similar manner by attending the massive celebrations in Achashverosh's palace where all sorts of food, drink, and diversions were available. His very intention was to evoke the Original Sin and bring about the Jews' destruction in the same way that the original sin caused that all of Mankind became mortal, starting with Adam himself.
It is at this point we see the wonders that the Creator effected!
That Haman cast lots to determine which month would be most fortuitous to carry out his plot and landed on Adar was in fact the turning point! Adar, which corresponds to the nose, the organ that enables the sense of smell, the only sense that was not blemished by that Original Sin that Haman tried to recall and repeat; this is why it is called Purim because Haman's lottery proved to be fortuitous for us, not him! The sense of smell that is completely spiritual - that is called a ko'ach niskayemet - as represented by the month of Adar remains unblemished still, and protected the Jews again from annihilation.
This sense of smell is a dominant theme in Purim especially: Mordechai's name can be broken down as mara dechai one of the ingredients of the ketoret; Esther's true name Hadassah is a fragrant leaf that is often included in the besamim of Shabbos Kodesh...
There is much to be said about these themes. For much more, see the writings of the B'nei Yissaschar on Chodesh Adar.