The Rambam’s Mishneh Torah
While Sefer Devarim is the first book to be called Mishneh Torah, it certainly is not the last. More than 2,000 years later, the Rambam (1138-1204) would write a set of books of Halachah, which he also called Mishneh Torah. Why did he choose that name?
Well, no need to guess. In the words of the author, here’s how Rabbi Moshe the son of Maimon explained it in his introduction to the 14-volume set:
I therefore named this set Mishneh Torah, “second [to the] Torah,” since a person can read the Written Torah and then read this and know the entire Oral Tradition, without having to read any other books between them.
Rambam, Introduction to Mishneh Torah
BTW: These words of the great Rambam shook the “Torah World.” They found it hard to believe that the Rambam would write these words! But he did. Think about it.