2Jeff Smith = "Chabad.org breaks down the history of the hamantaschen in a long, well-written article celebrating Purim. Here is an excerpt:Although nowadays you can find hamantaschen filled with practically any type of filling (sweet or savory), the classic hamantash was always filled with poppy seeds. Indeed, the very word “haman” can either refer to the wicked Haman or poppy seeds (mohn), and the Yiddish word“tash” means pocket. Thus, “hamantaschen” means “poppy-seed-filled pockets.”This is in line with the classic explanation given in the Code of Jewish Law for eating hamantaschen on Purim:
Some say that one should eat a food made out of seeds on Purim in memory of the seeds that Daniel and his friends ate in the house of the king of Babylon, as the verse states, “And he gave them seeds.”But what in the world does Daniel eating seeds have to do with Purim?The Talmud explains that Hatach, Queen Esther’s faithful messenger and one of the lesser-known heroes of the Purim story, is a pseudonym for none other than Daniel.Furthermore, as we read in the Purim story, when Esther was in the king’s palace, she kept her identity secret. The Talmud explains that since the food was unkosher, she survived on various beans and seeds.It is in commemoration of both Daniel and Esther that there is a custom to eat beans and seeds on Purim. The way this custom is traditionally observed is by eating pastry pockets, a.k.a. taschen filled with mohn, poppy seeds.Based on this reason for eating hamantaschen, whenever the classic halachic sources discuss this custom, specific mention is made of the hamantash being filled with poppy seeds.In addition to the classic reason for hamantaschen, many other explanations have been offered to explain this custom. Indeed, just about every aspect of this treat is laden with symbolism."