Arain Caste?? Help solving the mystery?

bitter, I think you meant to say Arain not Arians. (Arians were a Christian sect that did not believe in the Trinity)

As far as foreign origins are concerned. Some people do claim foreign descent. Usually, this is because their parents tell them they are descendants of foreigners. Historically, Islam came to India at the hand of middle eastern/ central asian invaders. Many of us claim descent from them. The reasons for such lies are complex, and not a simple self esteem issue, in my opinion. For example, in the early days of Islam, during the Umayyid period, converts to Islam were expected to pay both jizya and zakat. Effectively, one's conversion to Islam was denied, unless one was affiliated with the Southern Arab tribes. The unintended consequnce of such a policy of aparthied are obvious, people began falsely claiming descent from Souther Arab tribes (to avoid paying double taxes). These prejudices I believe linger till today. After all, those non arabs who told their children they were descendants of arab tribes were hardly going to tell future generations they lied. In most cases that knowledge was probably lost after the first generation, any way. Similar thing probably happened during the central asian invasion of India.

That said, we should all keep in mind that according to the DNA evidence everyone came to India from somewhere. We all share a common ancestor (proverbial Adam) who lived in Africa about 75,000 years ago. His descendants came out of Africa in different waves at different times. Very few have paternal ancestors who came to India 50k ago, just as very few have ancestors who came more recently, after Islamic invaders conquered India.