According to John Tvedtnes, the Hebraisms in the Book of Mormon help persuade us that it is authentic. The following story will illustrate:
During the years 1968-71, I taught Hebrew at the University of Utah. My practice was to ask new students to respond to a questionaire, giving some idea of their interests and linguistic background. One student wrote that she wanted to study Hebrew in order to prove the Book of Mormon was a fraud. She approached me after class to explain.
When I inquired why she felt the Book of Mormon was fraudulent, she stated that it was full of errors. I asked for an example. She drew my attention to Alma 46:19, where we read, "When Moroni had said these words, he went forth among the people, waving the rent part of his garment in the air." She noted that in the 1830 edition (p. 351), this read simply "waving the rent of his garment." In English, the rent is the hole in the garment, not the piece torn out of the garment. Therefore, Moroni could not have waved it. This was an error, she contended, and adding the word part later was mere deception.
This was my first introduction to variations in different editions of the Book of Mormon. Without a Hebrew background, I might have been bothered by it. But the explanation was clear when I considered how Mormon would have written that sentence. Hebrew does not have to add the word part to a verbal substantive like rent as English requires. Thus, broken in Hebrew can refer to a broken thing or a broken part, while new can refer to a new thing. In the verse the student cited, rent would mean rent thing or rent part. Thus, the "error" she saw as evidence of fraud was really a Hebraism that was evidence for the authenticity of the Book of Mormon.
Significantly, the first (1830) edition of the Book of Mormon contains many more Hebraisms than later editions. Later editions, especially in 1837, 1840, and 1876, were edited to improve the English areas where the text appeared to be awkward. Unfortunately, this destroyed some of the evidence for a Hebrew original. [John A. Tvedtnes, "The Hebrew Background of the Book of Mormon," in Rediscovering the Book of Mormon, F.A.R.M.S., p. 78]