I'm not sure if the Arab Christians find the term Nasrani insulting because of its connection with a heretical sect or because it is simply the name Muslims have used for them throughout history as their rulers have tried to reduce them to dhimmitude. It is generally accepted that the term just means "Nazarene"; Christians of Syriac rites historically refer to themselves as Arabic Masihi/East Syriac Mshihaya/West Syriac Mshihoyo, "Christian," from Masih/Mshiha/Mshiho, "Christ, Messiah." The St. Thomas Christians of Kerala are known among themselves as Nasrani or Mar Thoma Nasrani.
I'm not sure if the Nazarene sect was actually still around at the time of Muhammad or not (Epiphanius of Salamis mentions a sect by that name in the 4th century); they were Judaizers who kept the ceremonial prescriptions of the Old Law. The variety of Christianity in Arabia at the time of Muhammad is only dimly understood, as it was something of a cultural backwater; the great centers of Syriac learning were in modern-day Syria, Iraq and Turkey. There are legends of Muhammad learning the basics of Christianity from a Nestorian monk, though the Qur'an's understanding of Christian doctrine doesn't seem distinctly Nestorian. Muhammad seems either to have learned from a heretical sect or misunderstood what he heard; the Qur'an (Surah 5:116) seems to suggest Mary is a deity, with some suggesting that Muhammad thought Mary was the Third Person of the Trinity. The Qur'anic verse probably refers to Christian veneration of images of the Theotokos; later commentators more explicitly say Mary is part of the Trinity.
Last edited by MalpanaGiwargis; 07/26/14 06:45 PM. Reason: Misleading wording.