Their customs, like their tenets, display a remarkable catholicity. They baptize, circumcise, reverence the sun and moon, carve Musulman texts upon their tombs, quote the New Testament, allow polygamy, consider wine lawful, and certain meats forbidden, a mixture of the habits of Zoroaster, Assyrio-Babylonian, Muhammadan and Christian worship unequalled by any other sect. They abhor the colour blue, and never use it in their dress nor display it in their houses.
The centre and apparently original seat of these people is near Mosul, and there, in a valley of the Kurdish hills, is buried the Yezidi saint and prophet, Shaikh Adi, who is said to have lived variously in the ninth and eleventh century.
Very little has hitherto been known about Shaikh Adi, the date of his existence is disputed, and his identity has not been even hinted at, except for an ingenious theory put forward many years ago, attempting to connect him with Adde, a discipline of Manes.
So far we have had to be content with the assertion advanced in a Persian work that he was one of the Marwanian dynasty of Khalifas or “Caliphs,” an error easily discovered.
I think, however, that the following explanation may be now accepted, the result of investigations in various Muhammadan works, to the authors of which he is well known.
From these the writer has extracted the information that Shaikh Adi was the son of Musafiru’ Zahid, of the family of Ummaya, a native of Baalbek in Syria. In the reign of Marwan (early eighth century), he “was transferred” to Mosul,[20] and resided in the towns of the great Kurdish tribe of Hakkari, where his great sanctity gained him a large following among the peoples there residing.
He died during his exile, and was buried in a valley called Lash,[21] which means in Kurdish “the place of a body,” probably a name given after the interment.
There are four ranks in the priesthood of the Yezidis: Pir, Shaikh, Qawwal, and Faqir. The first, a Kurdish and Persian word signifying an elder or a saint, are persons of great sanctity and abstention. The Shaikhs (leader, chief), correspond to resident priests, while the Qawwal (speaker) are itinerant, and are expected to sing and dance in the festivals which demand those exercises. The last order, the Faqir (poor, humble), perform menial tasks in attendance upon the tomb of Shaikh Adi, at the valley of that name near Mosul.
The language used is a Kurdish dialect, but Arabic is employed in their chants and hymns.
A great deal of mystery surrounds their origin, and, as reading and writing are considered crimes among them, documents do not exist to help speculation. Layard imagined them to be Chaldean by origin, who have adopted the outward forms of many religions as a protective measure, and incidentally fallen into confusion regarding their own tenets.