In response to his life-changing vision, Alma exclaimed:
My soul hath been redeemed from the gall of bitterness and bonds of iniquity. I was in the darkest abyss; but now I behold the marvelous light of God. My soul was racked with eternal torment; but I am snatched, and my soul is pained no more. (Mosiah 27:29)
According to Hugh Nibley, there is your definition of "eternal torment." You might ask, "Well, how could Alma be out of it? It was eternal. If his soul was racked with eternal torment, he would still be there, wouldn't he?" No, he said, I'm out of it now, "I am snatched, and my soul is pained no more." That means the torment by nature is eternal. Anybody who qualifies for it [eternal torment] will get it from now to the end of time. It's there all the time, not that you have to suffer it all the time. This is one of the errors of christian theology. According to them it's eternal torment, meaning that once you go to hell, it's eternal--forever and forever. Well, Alma had been as most people who go to hell, but it's not eternal. He gets out of it now. [Hugh W. Nibley, Teachings of the Book of Mormon, Semester 2, p. 194]
So once again we see that the Book of Mormon was not just a part of Joseph Smith's Protestant environment.