Origin of the Kurds

Scholars have suggested different theories for the origin of the name "Kurd". According to the English Orientalist Godfrey Rolles Driver, the term "Kurd" is related to the Sumerian "Karda" which was found from Sumerian clay tablets of the third millennium B.C, while according to other scholars, it predates the Islamic period, as a Middle Persian word for "nomad", and may ultimately be derived from an ancient toponym or tribal name, either that of the "Cyrtii" or of "Corduene".
Name.
There are different theories about the origin of name "Kurd". According to one theory, it originates in Middle Persian as 𐭪𐭥𐭫𐭲 "kwrt-", a term for "nomad; tent-dweller".
After the Muslim conquest of Persia, this term is adopted into Arabic as "kurd-", and was used specifically of nomadic tribes.
As for the Middle Persian noun "kwrt-" originating in an ancient toponym, it has been argued that it may ultimately reflect a Bronze Age toponym "Qardu", "Kar-da", which may also be reflected in the Arabic (Quranic) toponym "Ǧūdī" (re-adopted in Kurdish as "Cûdî"). From the 7th century onwards, the name Kurd is better known, since the Arabs used it often (al Akrad). 
According to some sources, by the 16th century, there seems to develop an ethnic identity designated by the term "Kurd" among various Northwestern Iranian groups, without reference to any specific Iranian language.
Kurdish scholar Mehrdad Izady argues that any nomadic groups called "kurd" in medieval Arabic are "bona fide ethnic Kurds", and that it is conversely the non-Kurdish groups descended from them who have "acquired separate ethnic identities since the end of the medieval period".
Sherefxan Bidlisi in the 16th century states that there are four division of "Kurds": "Kurmanj", "Lur", "Kalhor" and "Guran", each of which speak a different dialect or language variation. Paul (2008) notes that the 16th-century usage of the term "Kurd" as recorded by Bidlisi, regardless of linguistic grouping, might still reflect an incipient Northwestern Iranian "Kurdish" ethnic identity uniting the Kurmanj, Kalhor, and Guran.
Ethnogenesis.
The term "kurd" is used in the 16th century by Sherefxan Bidlisi as encompassing four tribal groups, the "Kurmanj", "Lur", "Kalhor" and "Guran", each of which speak a different dialect or language variation. Paul (2008) argues that this marks an incipient ethnogenesis of the Kurds as a coherent Northwestern Iranian group, as three out of these four groups can be identified as the ancestors of groups that at least partially identify as Kurdish today, while the "Lurs" are not a Kurdish group, and indeed do not belong to the Northwest Iranian but to the Southwestern Iranian linguistic phylum. Paul further notes that the first texts that identifiably are written in Kurdish appear during the same period.
Predecessor groups.
The Kurdish people are believed to be of heterogeneous origins combining a number of earlier tribal or ethnic groups 
including Lullubi, Guti, Cyrtians, Carduchi.
Some of them have also absorbed some elements from Semitic, Turkic and Armenian people.
Kurds are an Iranian people, and the first known Indo-Iranians in the region were the Mitanni, who established a kingdom in northern Syria five centuries after the fall of Gutium. The Mitanni are believed to have spoken an Indo-Aryan language, or perhaps a pre-split Indo-Iranian language. The current view is that the separation of Iranian peoples from Indo-Aryans occurred between 1800 and 1600 BCE, which makes it nearly impossible for the Gutians to have been linguistically or culturally Kurdish, although it is possible that they still contributed to the Kurdish ethnogenesis to an extent, if at the very least genetically.
19th-century scholars, such as George Rawlinson, identified Corduene and Carduchi with the modern Kurds, considering that "Carduchi" was the ancient lexical equivalent of "Kurdistan". This view is supported by some recent academic sources which have considered Corduene as proto-Kurdish or as equivalent to modern-day Kurdistan. Some modern scholars, however, reject a Kurdish connection to the Carduchi.
There were numerous forms of this name, partly due to the difficulty of representing "kh" in Latin. The spelling "Karduchoi" is itself probably borrowed from Armenian, since the termination "-choi" represents the Armenian language plural suffix "-kh". It is speculated that Carduchi spoke an Old Iranian language. They also seem to have had Armenian elements. 
Jewish sources trace origins of people of Corduene to marriage of Jinns of King Solomon with 500 beautiful Jewish women. The same legend was also used by the early Islamic authorities to explain origins of Kurds.
The Medes have often been believed to be a starting point for Kurdish (as well as Baloch) ethnogesis. This would leave about a millennium of separate development between the collapse of the Median Empire and the first historical mention of the Kurds as an identifiable ethnic group.
The Median hypothesis was advanced by Vladimir Minorsky. I. Gershevitch provided "a piece of linguistic confirmation" of Minorsky's identification and then another "sociolinguistic" argument. Gernot Windfuhr (1975) dentified Kurdish dialects as Parthian, albeit with a Median substratum. The hypothesis is supported by Martin van Bruinessen. 
Origin legends.
There are multiple legends that detail the origins of the Kurds. One details the Kurds as being the descendants of King Solomon’s angelic servants (Djinn). These were sent to Europe to bring him five-hundred beautiful maidens, for the king's harem. However, when these had done so and returned to Israel the king had already died. As such, the Djinn settled in the mountains, married the women themselves, and their offspring came to be known as the Kurds.
Additionally, in the legend of Newroz, an evil king named Zahak, who had two snakes growing out of his shoulders, had conquered Iran, and terrorized its subjects; demanding daily sacrifices in the form of young men's brains. Unknowingly to Zahak, the cooks of the palace saved one of the men, and mixed the brains of the other with those of a sheep. The men that were saved were told to flee to the mountains. Hereafter, Kaveh the Blacksmith, who had already lost several of his children to Zahak, trained the men in the mountains, and stormed Zahak's palace, severing the heads of the snakes and killing the tyrannical king. Kaveh was instilled as the new king, and his followers formed the beginning of the Kurdish people.
In the writings of the Ottoman Turkish traveller Evliya Çelebi, there's also a legend concerning the Kurds to be found. He states to have learned of this legend from a certain "Mighdisî", an Armenian historian: