Joseph the Egyptian...
Joseph, son of Israel, and father of Ephraim and Manasseh, has a deep and abiding connection with the land of Egypt. It started with the jealousy of his brothers because of his father's preference of their younger brother. Their response was to throw him in a pit and kill him. Judah convinces his brothers that instead of killing him they should instead sell him into slavery.
28 Then there passed by Midianites merchantmen; and they drew and lifted up Joseph out of the pit, and sold Joseph to the Ishmeelites for twenty pieces of silver: and they brought Joseph into Egypt.
Once in Egypt, Joseph finds himself sold into the house of a Captain of the Guards named Potiphar, who sees that God is with Joseph and appoints him to be the chief steward of his house.
4 And Joseph found grace in his sight, and he served him: and he made him overseer over his house, and all that he had he put into his hand.
What, then, would be the responsibilities of the chief steward? He would have had the responsibility of ensuring that everything runs smoothly; food, water, money, even the master's wives and concubines. All of these responsibilities would have required a mastery of the Egyptian language, both spoken and written, even though that would not have been his native language. Later, as Joseph is put into prison because of Potiphar's wife, he is again placed into a position of responsibility, as overseer of everything in the prison.
21 ¶But the Lord was with Joseph, and shewed him mercy, and gave him favour in the sight of the keeper of the prison.
22 And the keeper of the prison committed to Joseph’s hand all the prisoners that were in the prison; and whatsoever they did there, he was the doer of it.
23 The keeper of the prison looked not to any thing that was under his hand; because the Lord was with him, and that which he did, the Lord made it to prosper.
Once again, Joseph would need a mastery of the Egyptian language, both written and spoken, in order to accomplish the tasks assigned to him. At this point he is taken before Pharaoh and interprets Pharaoh's dream. Once again, he is placed into a position of responsibility in Pharaoh's court, which would, again, require him to be fluent in written and spoken Egyptian. It is of interest to me that he is taken through sever different levels of both Egyptian society, as well as the governmental bureaucracy of Pharaoh and his kingdom. He starts with a soldier, albeit a high ranking one, and then is moved to overseeing a large government facility, and finally as a steward of Pharaoh. His language skills, after all this time in Egypt, would have been formidable, but more importantly, would have been comfortable to him. I experienced something similar when I served my mission in Spain, in the process of learning Spanish. To this day, I prefer to read my scriptures in Spanish, and I prefer to pray in Spanish. Joseph, after his family is gathered in, is given a position of responsibility over his family, and this preferred place is passed on to his children. When he was near death, Jacob called for Joseph and blessed his sons, but more importantly, we adopts Joseph's sons as his own:
5 ¶And now thy two sons, Ephraim and Manasseh, which were born unto thee in the land of Egypt before I came unto thee into Egypt, are mine; as Reuben and Simeon, they shall be mine.
6 And thy issue, which thou begettest after them, shall be thine,and shall be called after the name of their brethren in their inheritance.
Joseph and his children both lived and died in Egypt, and it wasn't until Moses led the Children of Israel out of Egypt. Ephraim and Manasseh (the tribes) are given their own lands in Canaan, and even formed their own kingdom after the death of King Solomon. In order to read and understand the records kept by Joseph in Egypt, it would have been necessary for some in these lands and kingdoms to maintain an understanding of the Egyptian language and writing systems. It is interesting, then, that when Nephi retrieves the plates of brass from Laban, he finds that they contain basically what we have in the modern Old Testament, up to 600 B.C. But there is something more on these plates:
14 And it came to pass that my father, Lehi, also found upon the plates of brass a genealogy of his fathers; wherefore he knew that he was a descendant of Joseph; yea, even that Joseph who was the son of Jacob, who was sold into Egypt, and who was preserved by the hand of the Lord, that he might preserve his father, Jacob, and all his household from perishing with famine.
15 And they were also led out of captivity and out of the land of Egypt, by that same God who had preserved them.
16 And thus my father, Lehi, did discover the genealogy of his fathers. And Laban also was a descendant of Joseph, wherefore he and his fathers had kept the records.
These plates were the records kept by the descendants of Joseph, and were passed on to specific people (such as Laban). Lehi, and his son Nephi are also in the habit of keeping records on plates of metal, these records are written in a form of Egyptian, and are maintained by descendants of Joseph (Manasseh). Some have criticized the Book of Mormon, and Joseph Smith, for suggesting that "Jews" would use Egyptian to record their history and write their scripture. Some refer to Egyptian as the language of the "slave period" of the Jews, but it is actually the language used by the great Patriarch of the tribe of Joseph, and was continued by certain members of his family throughout the years after his death. What was once an anachronism has become an evidence in favor of Joseph Smith and the Book of Mormon.