“Haman, BOO! Haman, BOO!”
Haman was King Ahasuerus’s right hand; a wicked villain who plotted to kill Mordecai and the Jewish people. During the reading of the megillah (‘scroll,’ here referring to the scroll in which the Book of Esther is written) we blot out Haman’s name with boo’s, stomps, and noisemakers. Folklore has it that Haman wore a three cornered hat and that that is why we eat the triangular cookies called hamantaschen on Purim.