"The bilingualism of the book of Daniel is not unique in the Old Testament.
The same phenomenon is found in the book of Ezra.
Ezra 4:8–6:18 and 7:12–26 are written in Aramaic, while the rest of the book is written in Hebrew.
---However, the explanation of the usage of two languages in Ezra is much more obvious and has not generated a bulk of different views. The Aramaic portions of the book of Ezra mainly contain letters and documents that were originally written in Aramaic, and the author decided not to translate them but, rather, presented them in the original language. Since most of those returning from the Babylonian captivity understood the Aramaic language, it was very appropriate to cite letters and documents in the original language.
Daniel starts the book in Hebrew but, beginning with Daniel 2:4, he shifts to Aramaic and continues in it until the end of chapter 7. Then, beginning with chapter 8, he resumes in Hebrew. However, when it comes to the very last word of the book, we discover something interesting. Daniel starts the last word in Hebrew but adds to it an Aramaic ending. It appears as if in the last word, he tries to connect the two languages employed in the book.
Gleason Archer states, “A careful study of the subject matter yields fairly obvious answers: The Aramaic chapters deal with matters pertaining to the entire citizenry of the Babylonian and the Persian empires, whereas the other six chapters relate to peculiarly Jewish concerns and God’s special plans for the future of his covenant people.”
----The very last Hebrew word of the book of Daniel is unique because of its Aramaic plural ending and because of its strong eschatological context. Naturally, it puzzles students of the book. Why does Daniel add to a Hebrew word an Aramaic ending?
.....two possibilities.
First of all, since Daniel used the two languages throughout the book, the combination of the two languages in the very final word would send a signal to the readers that it was one writer who authored both parts of the book. The final word, in a way, underlines the unity of the Hebrew and Aramaic sections of Daniel.Second, but no less important, the prophet attempts, through the last word, to safeguard the readers from a wrong interpretation of the text. If Daniel would use a normal and expected Hebrew ending to the Hebrew word for “days,” it would significantly alter the meaning. One naturally asks, when will the promised resurrection of Daniel actually occur? At the end of which days? Looking at the context of Daniel 12:13, the reader will quickly realize that the text immediately preceding (v. 12) refers to the blessing given those who will reach the 1,335 days. Here, for “days” Daniel employs a Hebrew word with a Hebrew plural ending.
If, in the very next verse, Daniel used the same Hebrew word with the same Hebrew plural ending that he used in Daniel 12:12, the reader would conclude that the phrase which follows—“at the end of the days” (referring to the 1,335 days)—points to the very end of the 1,335 days. It would mean that the promised resurrection will occur at the end of the 1,335 days. That would seem to support those advocating a futuristic approach to the interpretation of the eschatological prophecies. However, the usage of an Aramaic ending to the Hebrew word for “days” differentiates it from the 1,335 days. It is also significant to note that in verse 13, Daniel adds to the word “days” a definite article, which additionally points to the special “end” of the days and supports a differentiation from the 1,335 days."ArturStele/Ministry
