For years, critics have pointed to Joseph Smith’s use of Elijah and Elias as names or designations for distinct individuals as evidence that he was a false prophet. After all, Elias is simply a Greek transliteration of the Hebrew name of the prophet Elijah. In his cunning ignorance, so the argument goes, Joseph unwittingly manufactured two different individuals out of the single historical Eliyahu (אֵלִיָּהוּ).
Of course, it strains credulity — at least, it does so for me — to try to imagine the creator of the Book of Mormon (as such critics typically take him to be) as a blithering idiot who knew essentially nothing about the Bible.
But here’s a nice perspective on the subject from the estimable Robert Boylan, in Ireland:
http://scripturalmormonism.blogspot.com/2014/08/elias-as-forerunner-in-lds-scripture.html