Hamantashen is Yiddish for "Haman's pockets". They are meant to recall the story of Haman, a wicked Persian prince who wished to destroy the Jews but was foiled by Mordecai and Esther." They are cookies filled with various fruits and other ingredients.

In Hebrew, Hamantashen are better known as Oznay Haman (sorry about the likely incorrect spelling, but this is the best I can do phonetically). As far as I remember, this means the ears of Haman, and they are triangular because the ears of Haman were triangular according to legend (like elves, or Vulcans). This is contrary to the write-up under Haman, which states that the Hamantashen are triangular because of Haman's triangular hat. However, since Oznay means ears if I remember correctly, ears are the most likely explanation.

Or not. Maybe this Haman guy really liked triangles.

Traditionaly, the cookies are filled with poppy seeds or jam.