In Persian mythology, Dahāka is treated as a proper noun, while the form Zahhāk, which appears in the Shāhnāme, was created through the influence of the unrelated Arabic word ḍaḥḥāk (ضَحَّاك) meaning "one who laughs".

The name also migrated to Eastern Europe,[9] assumed the form "ažhdaja" and the meaning "dragon", "dragoness"[10] or "water snake"[11] in Balkanic and Slavic languages.

[citation needed] Aži Dahāka appears in several of the Avestan myths and is mentioned parenthetically in many more places in Zoroastrian literature.

[citation needed] In a post-Avestan Zoroastrian text, the Dēnkard, Aži Dahāka is possessed of all possible sins and evil counsels, the opposite of the good king Jam (or Jamshid).

Based on the similarity between Baβri and Old Persian Bābiru (Babylon), later Zoroastrians localized Aži Dahāka in Mesopotamia, though the identification is open to doubt.

Together they attack the hero Yima (Jamshid)[clarification needed] and cut him in half with a saw, but are then beaten back by the yazata Ātar, the divine spirit of fire.

The Avesta identifies the person who finally disposed of Aži Dahāka as Θraētaona son of Aθβiya, in Middle Persian called Frēdōn.

The Avesta has little to say about the nature of Θraētaona's defeat of Aži Dahāka, other than that it enabled him to liberate Arənavāci and Savaŋhavāci, the two most beautiful women in the world.

Feyredon is said to have been endowed with the divine radiance of kings (Khvarenah, New Persian farr) for life, and was able to defeat Dahāg, striking him with a mace.

However, when he did so, vermin (snakes, insects and the like) emerged from the wounds, and the god Ormazd told him not to kill Dahāg, lest the world become infected with these creatures.

[citation needed] In Ferdowsi's epic poem, the Shāhnāmah, written c. 1000 AD and part of Iranian folklore, the legend is retold with the main character given the name of Zahhāk and changed from a supernatural monster into an evil human being.

When Zahhāk is a young man, Ahriman first appears to him as a glib, flattering companion, and by degrees convinces him to kill his own father and inherit his kingdom, treasures and army.

Two men, called Armayel and Garmayel, seek to rescue people from being killed from the snakes by learning cookery and becoming Zahhāk's royal chefs.

Each day, Armayel and Garmayel save one of the two men by sending him off to the mountains and faraway plains, and substitute the man's brain with that of a sheep.

The youngest warrior knocks Zahhāk down with his mace, ties him up, and drags him off toward Mount Damāvand as a large crowd follows.

His hesitant counsellors remain silent until the most fearless of the men reports that the dream is a vision of the end of Zahhāk's reign at the hands of Fereydun, the young man with the mace.

However, a blacksmith named Kāva (Kaveh) speaks out in anger for his children having been murdered to feed Zahhāk's snakes, and for his final remaining son being sentenced to the same fate.

"Zahhak Castle" is the name of an ancient ruin in Hashtrud, East Azerbaijan Province, Iran which according to various experts, was inhabited from the second millennia BC until the Timurid-era.

[18][19] Besides Aži Dahāka, several other dragons and dragon-like creatures are mentioned in Zoroastrian scripture: Stories of monstrous serpents who are killed or imprisoned by heroes or divine beings may date back to prehistory and are found in the myths of many Indo-European peoples, including those of the Indo-Iranians, that is, the common ancestors of both the Iranians and Vedic Indians.

Thus, although it seems clear that dragon-slaying heroes (and gods in the case of the Vedas) "were a part of Indo-Iranian tradition and folklore, it is also apparent that Iran and India developed distinct myths early."