In the Book of Mormon Nephi refers to himself as a Jew, such as in 2 Nephi 33:8
I have charity for the Jew—I say Jew, because I mean them from whence I came.
Why would Nephi consider himself a “Jew” if he was of the tribe of Manasseh?
Book of Mormon Central explains:
The word Jew can be traced to the Hebrew word Yehudi and, contrary to the previously mentioned assumption, was actually used during Pre-exilic times. It was originally applied to members of the tribe of Judah, but after the division of Solomon’s Kingdom (into the northern kingdom of Israel and the southern kingdom of Judah), the term Jew was applied more generally “to all residents of the Southern Kingdom, irrespective of their tribal status.” The term is used in this political sense by the historian of the book of Kings (2 Kings 16:6; 25:25).– Book of Mormon Central – Was Nephi Really A Jew?
How did Joseph Smith know that Nephi would consider himself a Jew politically?