The Arab villages are Beshiqe and Behzani, they are 30 km far from Mosul, and are like 'twin villages'. The interesting point is that their Arabic is near to Lebanese Arabic, not an Iraqi Arabic, and Sheikh Adi was originated from Lebanon (that was called Syria at his time). These Arab Yezidi clamed to be arrived in Kurdistan since 12th century with Sheikh Adi, but of course, there are no proof of that except this Lebanese Arabic.
Another interesting point is that they are qewel (religious singers) and their ritual dresses are undoubtedly Arabic, though the religious songs are in Kurdish. And their place in religious celebration is important.
So there could have many explanations :
– There could have been assimilated by their Arab neighbors, but in that case, it is strange they speak Lebanese and not Iraqi, as other Mosuli.
– Sheikh Adi came from Lebanon not alone, he was the leader of 'Adawiya order, a sunni sufi tariqet, which had a branch in Cairo. His first companions should be ethnically mixed, and of courses his family or relatives were Arabs.
– At the time of its expansion, Yezidism was not an 'ethnic' religion, some Arabs could have been converted with Kurds.
– At last, these Arab Yezidis have their own explanation and I let you discover it in the text

It is also explained why the price of their bride is so expansive when a Kurdish Yezidi ask one of their daughter.
It is an interesting fact for Yezidi studies, I type all the passage, but I recommend to read all the book, who is not too long and very interesting, written by a Jewish Hungarian scholar, who speak kurmanji and spent many months and even years among Yezidis in Kurdistan :
The villages of Beshiqe and Behzani, a mere thirty kilometers from Mosul, constitute a unique case deserving special attention. Although described as belonging to the Sheikhan area by most book dealing with Yezidis, the inhabitants of the two villages at the feet of Mount Meqlub, which isolates them from the rest of Sheikhan, see themselves and are seen by other Yezidis as a distinct entity. These twin villages, today separated only by an asphalt road in the middle of the settlement, are the villages of the Yezidi qewel, or religious singers, keepers of the ancient lore who must by the force or tradition make their dwelling in either of these two villages. Perhaps due to the presence of the qewels, the people of Beshiqe-Behzani are traditionally more devoted to religious duties and education than other settlements. The Yezidis of the twin villages serves as xizmetkar, servitors in the Sanctuary of Sheikh Adi in the sacred valley of Lalish; in other word, it is their duty to go several times a year, before and after major holidays, to maintain the holy precincts. The first Yezidi school to teach children the previously forbidden arts of reading and writing was founded in Beshiqe by Mayan Khatun, the Yezidi 'motehr queen', in the first half of the twentieth century. Today the only Yezidi 'Sunday school', the sole aim of which is to teach Yezidi children about their faith and help them to memorize some of the sacred texts, is in the same village. It was founded a few years ago, semi-clandestinely, in the face of the official ban of the Saddam government on anything 'smacking of Kurdishness'.
Interestingly enough, while the religious hymns and prayers entrusted to the memory of the qewels are all in Kurdish, the inhabitants of the two villages speak Arabic as a mother tongue – alone along the Yezidis. Nor is this the Arabic of Northern Iraq, or even in Iraq. According to the people of Beshiqe-Behzani, the Arabic they speak is closest to that of Lebanon (and they certainly show a predilection for watching Lebanese TV. They claim to have arrived from the Beka'a Valley in Lebanon in the twelth century with Sheikh Adi. Accordingly, they term themselves tazhi (meaning 'greyhounds', the only kind of dog that enjoy respect among Kurds) – a term that refers to their loyalty to their leader. (Scholars, on the other hand, say that the word is a corrupted form of tazî, Kurdish for 'naked' and simply means 'Arabs' in this context.)
This is not the only Kurdish word they use, however. Behzani Yezidi claim that their language contains ancient Kurdish words no longer in use among other Kurdish speakers. They explain by saying that originally they were Kurds who migrated to Lebanon and then returned centuries later with Sheikh Adi. This is an explanation that may perhaps lack any historical or linguistic foundation, but one that certainly adds an interesting detail to the much-debated question of Yezidi national identity.
Beshiqe-Behzani, with its tight-packed streets of stone houses, reminiscient of Mediterranean fishing villages, differs from other Yezidi communities not only in its language and architecture, but in many other ways as well. A slight tension can be detected between the rest of the Yezidis and the inhabitants of the twin villages, who tend to look down on other Yezidis as less educated and more conservative. he twin villages have always been reluctant to give their daughters to Yezidis from other regions, whom they accuse not only of being backward but also of not treating their women well enough. Even if a bride is granted, her family asks for a shockingly high bride price from the 'outsider', while it would be shameful to ask for a bride price from a potential groom from Beshiqe or Behzani