Why is the holiday called Purim?

Purim comes from the word "pur" which means "lots." The book of Esther
tells us that upon receiving permission to annihilate the Jewish
people, Haman cast "lots" for the best day and month in which to
execute his plan, and the lot fell on the 13th day of the month Adar.
Knowing that Moses, the leader of the Jewish people, died in the month
of Adar, Haman thought that it must be an unlucky month for the Jews,
but he didn't know that Moses' date of birth was also in the month of
Adar. It turned out to be a good month for Israeland the month of
Haman's downfall.

Why is Yahveh's Name not mentioned in the Megilah?

The Rabbis explain that all other Jewish holidays celebrate miracles
which clearly showed Yahveh's involvement. The Purim miracle, however,
seemed to be "hidden" - yet looking closely, we can clearly see
Yahveh's Hand throughout. In keeping with the hidden nature of this
miracle, Yahveh's Name is not to be found in the Megilah in a revealed
way.

Another possible reason Yahveh is not mentioned in the book of Esther
is that the story of Purim was also entered into the records of Persia
and Mordechai and Esther wanted to make sure that the scribes of the
land will not replace Yahveh's name with names of their idols instead.

Mordechai and Esther both played a role in the story of Purim. So why
is the Megilah called "Megilat Esther - Scroll of Esther" only?

The Bible tells us that Esther's Jewish identity was originally not
known, so her life was not affected by Haman's decree. In spite of
this, Queen Esther risked death by revealing her Jewish identity in
order to plead for her people. Since Esther put her life in danger,
the Megilah was named after her.