|The Peacock Angel, Melek Taus|
The origin of the name of the group itself underscores some of the issues in the area. Linguists think it derives from Yezd, an ancient Persian word for "Supreme Being," or yazata, Iranian for "divine being." The usual story, however, is that they call themselves after the Umayyad Caliph Yazid I (also known as Yazīd ibn Mu‘āwiya; 647 - 683). An argument for this origin is made in an 1852 book* whose author describes their confessed desire to avoid persecution by Muslims:
The origin of the name of "Yezeedee," by which they are more commonly known, is referred by some among them to Yezeed ibn Moawiyah, but this is only a stratagem to secure their toleration by the Mohammedans. For a like purpose [...]. The quotation from the Koran near the tomb was also admitted by several Kawwâls to have been introduced as a blind, and in order to prevent the Moslems from desecrating; their sacred shrine.It appears that they have tried to fly "under the radar" of Muslims for a long time.
Another origin is that they were founded by Yezid ibn Unaisa, a member of a subject of Islam. Or they were started by a Sufi leader known as Sheik Adi bin Musafir who died in 1162.
The Yazidi believe in one god who created the world and left it to the care of seven angels. The most important of these is the angel Melek Taus, the "Peacock Angel." Sheik Adi was supposed to be a representative of Melek Taus on earth. Melek Taus was created before the other angels, and told by God never to bow to anyone else. Melek Taus, however, upon encountering Man, recognized his greatness and bowed to him. As the "best and brightest" of the angels who went against God's decree, Melek Taus has been equated by Muslims with Satan/Lucifer, and for that reason alone the Yazidi would find themselves a target for Muslim persecution.
Yazidi beliefs show similarities to Christianity, Judaism, Zoroastrianism, Islam and Gnosticism. They believe they are descended from Adam, but not from Eve; rather, through Adam's son Shehid bin Jer.** They do not believe in Original Sin, but that humans possess both good and evil, and have the opportunity to choose; just as Melek Taus chose good by bowing to Man.
They have restrictions and taboos that govern castes (marrying outside your caste is a capital offense), food, and the need to live in a Yazidi community rather than with outsiders. They also believe that souls can reincarnate when needed, using the metaphor of changing a dirty garment for a clean one. Moreover, they believe that the seven angels are capable of incarnating in human form when needed (just as they believe Sheik Adi was Melek Taus). They pray five times a day.
As of this writing (8 August 2014), the majority of Yazidi have fled Muslim persecution by trying to take a mountain route on foot to reach Dohuk in Iraqi Kurdistan. Humanitarian aid has been announced, as well as airstrikes against the pursuing ISIS army.
*An Inquiry into the Religious Tenets of the Yezeedes, by George Percy Badger
**A neat trick, whose explanation can be found in paragraph six on this site.