John A. Tvedtnes and Matthew Roper address the use of "Christians" in the Book of Mormon; the term was perhaps used to translate a word the Nephites would have used to denote a Messiah follower.
John A. Tvedtnes and Matthew Roper, "Response to Jehovah's Witness Articles on the LDS Church," 1997, Shields-Research.org, accessed February 22, 2023
"Acts 11:26 says: ‘The disciples were called Christians first in Antioch.' (KJ) But Alma 46:15, purportedly describing events in 73 B.C.E., has Christians in America before Christ ever came to earth" (p. 25). Were we to say that the Templars were organized in Germany and settled in the Holy Land in the late 19th century, you might try to correct us by saying that the Templars were organized in the year 1118 by Hugh de Payen and participated in a Crusade to the Holy Land in the years that followed. Actually, both statements are correct, for we would be referring to two different Christian groups that called themselves "Templars." Since Luke, who wrote the Acts of the Apostles, didn't know about the followers of Christ in the New World, he would naturally assume that the term "Christian" was first used in Antioch in his own day. In the same way, many history books credit Columbus with having discovered America, though there is now abundant evidence for the Vikings having visited North America five hundred years earlier. If one acknowledges that prophets such as Isaiah (e.g., Isaiah 53) foresaw the coming of Christ, there should be no problem in having a people living a few decades before his birth and who looked forward to his arrival calling themselves "Christians." Since the term "Christians" is from the Greek word that gave us "Christ," it would not, of course, have been used by the Nephites. They may have called themselves Meshihim, from the Hebrew Messiah. All we can say for certain is that the anglicized form "Christians" was used in the English translation to represent whatever term the Nephites used.