The designation "Nestorian" connotes both a religious rite and a linguistic minority, a phenomenon that is often misunderstood, especially by scholars but by many outsiders as well. This misunderstanding was dramatically illustrated in the aftermath of World War I, in the general lack of concern for the welfare of the Nestorians, both as an ethnic and as a religious entity.
Nestorians derive their name from Nestorius, who was bishop of Constantinople from 428 to 431, following the major controversy that split the early Christians over the nature of Christ: dual (human or divine) or singular (two in one, inseparable and closely bound together). They were influenced by the Antiochan writers of the preceding century, who emphasized Jesus' humanity with its inherent imperfections. But the real shaper of Nestorianism was Theodore (d. 428), bishop of Mopsuestia in Cilicia, who was a pupil of Diodorus, bishop of Tarsus. Theodore affirmed the true humanity of Jesus, arguing that he acquired his perfect sinlessness in union with the Person of the Divine Word, which he had received as a reward for his foreseen sinlessness. The Word, accordingly, dwelt in the man Christ (Hastings n.d.). Nestorians thus rejected the union of God and man in Christ. Mary was regarded as the mother of the man, not of God. It was not until Nestorius came to Constantinople that his teachings became popular and thus were named after him. Theodore's doctrine was formally condemned at the Fifth Ecumenical Council of Constantinople in 553.
Nestorians today, some 100,000 of them, have found a lasting home in the mountains of Kurdistan, the neighboring plains of Azerbaijan, in northwestern Iran, and in the mountainous region of eastern Turkey, in what is commonly referred to as Kurdistan. They are concentrated around Lake Urmia and in the low-lying plain of Mosul in northern Iraq, generally in close proximity to the Kurds, with whom they have had an on-and-off relationship throughout the centuries. Their great school was once located in Edessa (contemporary Urfa, in south-central Turkey).
Of complex ethnicity, Nestorians list in their ancestry Aramaeans, Assyrians, Kurds, Persians, and Arabs. After being Christianized, they came to be known as "East Syrians," to distinguish them from the "West Syrian" Monophysites or the Jacobites.