Demons, Dragons and Monsters in Persian Folklore

Daeva (daēuua, daāua, daēva) is an Avestan language term for a particular sort of supernatural entity with disagreeable characteristics. In the Gathas, the oldest texts of the Zoroastrian canon, the daevas are "wrong gods" or "false gods" or "gods that are (to be) rejected". This meaning is – subject to interpretation – perhaps also evident in the Old Persian "daiva inscription" of the 5th century BCE. In the Younger Avesta, the daevas are noxious creatures that promote chaos and disorder. In later tradition and folklore, the dēws (Zoroastrian Middle Persian; New Persian divs) are personifications of every imaginable evil.

Equivalents for Avestan daeva in Iranian languages include Pashto, Balochi, Kurdish dêw, Persian dīv/deev, all of which apply to demons, monsters, and other villainous creatures. The Iranian word was borrowed into Old Armenian as dew, Georgian as devi, in Tajik as dev, and Urdu as deo, with the same negative associations in those languages.

Sources: [1], [2], [3]