Coptic literature initially was influenced by Greek, especially in Alexandria where the Hellenistic culture was dominant.
Many church fathers had to write in Greek, the most prevalent language. Their writings were then translated into Coptic. Examples of purely Coptic literature are the works of Abba Antonius and Abba Pachomius, who only spoke Coptic, and the sermons and preachings of Abba Shenouda, who chose to only write in Coptic. Abba Shenouda was a popular leader who only spoke to the Copts in Coptic, the language of the repressed, not in Greek, the language of the repressive ruler.
Pure Coptic literature had two centers, Wadi al-Natrun and al-Dayr al-Abyad and the Pachom Monasteries in Upper Egypt. At Wadi al-Natrun, Coptic literature was written in the Bohairic dialect. In al-Dayr al-Abyad and the Pachom Monasteries in Upper Egypt.
Coptic was written in the Sahidic dialect. Thus, monasteries were the premier centers of Coptic literary output written in its two main dialects. In some of the manuscripts of the time, Coptic is called the language of the people of the mountains. This may refer to Upper Egypt where the altitude is higher and the monasteries were located up in the hills. The monastery of al-Dayr al-Abyad under Abba Shenouda in 383 AD became a center for Sahidic, the literary language of the Coptic Church in its golden years.
As the Coptic literary movement spearheaded by Abba Shenouda grew, Greek receded. In fact, the wane of the Greek language was in direct proportion to the spread of Christianity in the countryside, the increasing use of Coptic as a literary language, and the rise of the Copts, both in numbers and in their sense of self and community.
By the time the Arabs conquered Egypt, Sahidic was the general language of Coptic literature, while any spread in Bohairic in this period was related to translation activities of Sahidic literature, a phenomenon that was prevalent in the first six centuries of Christianity.