Earl M. Wunderli argues that "Christ" is an anachronism in the Book of Mormon; Joseph did not know "Christ" and "Messiah" are the Greek and Hebrew equivalents of the same word.
Earl M. Wunderli, An Imperfect Book: What the Book of Mormon Tells us About itself (Salt Lake City: Signature Books, 2013), 150-52
The Hebrew term “Messiah” was translated as “Christ” in the Greek New Testament, as spelled out explicitly in the Gospel of John: “Messias . . . is, being interpreted, the Christ” (John 1:41). The words both refer to the “anointed one,” which means the presence of the word “Christ” in the Book of Mormon is redundant. As one critic recognized, it is “a translation into Greek—a language with which the Nephites would not have been familiar—of a Hebrew word that the Nephites would have already understood.” A defender, who called this a tired “old argument,” replied that the Book of Mormon is “an English translation, and English has adopted a very large number of foreign words that, through time, have become acceptable English.” In Joseph Smith’s culture, Christ “was the preeminent term for ‘anointed one.’” That is not to say the gold plates “contained a Greek word or that the term rendered ‘Christ’ by Joseph Smith was foreign to pre-Christian Israelites.” Even so, it seems doubtful that the translation was loose.
It also seems doubtful that Joseph Smith knew that “Christ” was Greek for the Hebrew “Messiah” since the former is almost exclusively used as a name and the latter is employed only as a title in the Book of Mormon. Joseph did not know that these meant “the anointed one,” as one can tell from the unconventional use of “messiah.” In “traditional biblical writings,” Clark summarized, “Messiah is a transliteration of the Hebrew mashiah, meaning ‘anointed’ or, when referring to a person, ‘the anointed one.’ The Book of Mormon does not relate the term Messiah or anoint or any of its derivatives.” For example, Lehi prophesies to his sons regarding “a prophet . . . even a Messiah, or, in other words, a Savior of the world . . .Redeemer of the world” (1 Ne. 10:4-5). One must wonder why Lehi thought it necessary to define a Hebrew word to his Hebrew-speaking sons!