From Juan Cole's weblog:
.....Now-Ruz, the New Year celebrated by the Kurds (rooted in ancient Iranian Zoroastrianism, this holiday commemorates the spring solstice --usually March 21-- as the beginning of a new year). The Kurds tie their celebration to the legends of the Shahnameh, which tells the story of how in ancient times an evil ruler emerged, Dahhak or Zohak, who overthrew the glorious king Jamshid. Dahhak was a wizard who grew serpents on each of his shoulders, which needed to eat human brain every day. So Dahhak had young men rounded up from the subject populations, and two were sacrificed each day. Dahhak was finally overthrown by a young knight, Faridun, aided by the blacksmith Kaveh, who freed the captured young men on Now-Ruz. The Kurds have a legend that they are descended from those freed prisoners, and they celebrate their manumission on March 21. The story of Jamshid, Dahhak and Faridun is a variation on a widespread Indo-European myth cycle. In the ancient Indian sources the three are the king of the underworld, Yama; the world-serpent, Vrta, and Indra, who slays Vrta. The story is also echoed in the Nordic myth of Thor and the Midgaard serpent (Thor is a composite of Faridun the prince and Kaveh the blacksmith). At some point in Iran, the snake figure was historicized as an evil foreign king who brought drought and had serpents growing from his body, and he was also racialized. Dahhak or Zohak is a clearly Semitic word, whereas Jamshid and Faridun are Indo-Europeans. This development reflects the fights that took place when the Iranian peoples from Anatolia immigrated into Elamite and Assyrian territory in the 800s BC. Assyrians and Babylonians spoke Semitic languages related to Arabic and Hebrew. (Some US newspapers last year reported the struggle of Kaveh with Zohak as a historical event of the 7th century BC!)
The casting of the serpent monster as a Semitic ruler made it easy for Kurds to identify Dahhak with Saddam, and perhaps with the virulent strain of Arab nationalism he represented.