Ancient Kush extended across a large part of the Sudan. In this vast region encompassing the Napatan and Meroitic civilizations there were many different nationalities, that spoke a myriad of languages.
Due to the ethnic diversity of the Napatans, it is clear that at least from the Napatan period of Kush the rulers of the empire had decided that no single language spoken in the empire would be used to record political, administrative and religious information. To maintain an equilibrium within and among the Napatan nationalities Egyptian was used as the lingua franca of the empire.
The leaders of the Napatan empire probably used Egyptian because it was an international language, and few Kushites were of Egyptian ethnic origin.Egyptian remained the lingua franca for the Kushites during the Napatan and early Meroitic periods in Kushite history. After the Assyrians defeated the Egyptians the ethnic composition of the Kushite empire began to change. As a result, many Egyptians began to migrate into Kushite, to avoid non-Egyptian rule.
Beginning with the Assyrian defeat of the Twenty-Fifth Dynasty large number of nomadic people from the Middle East began to migrate into Egypt. These people began to take over many Egyptian settlements, while other Egyptians fled to Nubia and Kush to avoid non-Egyptian rule.Other political and military conflicts after the Assyrians led many Egyptians to migrate out of Egypt into Nubia and Kush. Herodotus’ mentions the mutiny of Psamtik I’s frontier garrison at Elephantine—these deserters moved into Kush.
Moreover, the archaizing trend in Kush among the post Twenty-Fifth Dynasty Kings testify to a possible large migration of Egyptians into Kush.In 343 BC Nectanebos II, fled to Upper Egypt. Later according to the Natasen period stela we evidence of other Egyptians migrating into Kush from Egypt (Torok, 1997, p.391).
Between the 260’s-270’s BC Upper Egyptian Nationalists were fighting the Ptolemy (Greek) rulers of Egypt. The rebellion was put down by Ptolemy II. This military action led to Egyptians migrating out of Egypt into Kush (Torok, pp.395-396). These rebellions continued in Egypt into the 2nd Century BC (Torok, p.426).
Between Ptolomy II and Ptolemy V, the Greeks began to settle Egypt. This was especially true in the 150’sBC and led to many Egyptians migrating back into Egypt. By the time the Romans entered Egypt, many Egyptians had already left Egypt and settled. Roman politics also forced many Egyptians to migrate into Kush. This was compounded by the introduction of the Pax Agusta policy of the Romans which sought the establishment of Roman hegemony within territories under Roman rule . This led to the emigration of many Romans into Egypt.The Kush was a multi-ethnic society. It included speakers of many languages within the empire.
During most of Kushite history the elites used Egyptian for record keeping since it was recognized as a neutral language.As more and more Egyptians, led by Egyptian nationalists, fled to Kush as it became under foreign domination the Egyptians formed a large minority in the Empire. Because of Egyptian migrations to Kush, by the rule of the Meroitic Queen Shanakdakheto, we find the Egyptian language abandoned as a medium of exchange in official records, and the Meroitic script takes its place.By the rise of Greeks in Egypt, the cultural ideology , like the people were changing.
This is supported by the transition from Demotic writing (7th 5th Centuries BC) to Coptic (4th BC-AD 1400). The Coptic people are the best evidence for the change in the Egyptian population.After the Egyptians became a sizable minority in Kush, the Kushites abandoned Egyptian as a lingua franca. Egyptian was replaced by the Meroitic writing.
Due to the fact that Meroite leaders were trying to maintain unity within the Meroitic Confederacy/Empire they did not record any ethnic lexical items in the Meroitic inscriptions , that I have read so far, except ethnonyms and toponyms.