The word “Lucifer” in Isaiah 14:12 presents a minor problem to mainstream Christianity. It becomes a much larger problem to Bible literalists, and becomes a huge obstacle for the claims of Mormonism. John J. Robinson in A Pilgrim’s Path, pp. 47-48 explains:
“Lucifer makes his appearance in the fourteenth chapter of the Old Testament book of Isaiah, at the twelfth verse, and nowhere else: “How art thou fallen from heaven, O Lucifer, son of the morning! How art thou cut down to the ground, which didst weaken the nations!”
“In the original Hebrew text, the fourteenth chapter of Isaiah is not about a fallen angel, but about a fallen Babylonian king, who during his lifetime had persecuted the children of Israel. It contains no mention of Satan, either by name or reference. The Hebrew scholar could only speculate that some early Christian scribes, writing in the Latin tongue used by the Church, had decided for themselves that they wanted the story to be about a fallen angel, a creature not even mentioned in the original Hebrew text, and to whom they gave the name “Lucifer.”
Why Lucifer? In Roman astronomy, Lucifer was the name given to the morning star (the star we now know by another Roman name, Venus). The morning star appears in the heavens just before dawn, heralding the rising sun. The name derives from the Latin term lucem ferre, bringer, or bearer, of light.” In the Hebrew text the expression used to describe the Babylonian king before his death is Helal, son of Shahar, which can best be translated as “Day star, son of the Dawn.” The name evokes the golden glitter of a proud king’s dress and court (much as his personal splendor earned for King Louis XIV of France the appellation, “The Sun King”).
The scholars authorized by … King James I to translate the Bible into current English did not use the original Hebrew texts, but used versions translated … largely by St. Jerome in the fourth century. Jerome had mistranslated the Hebraic metaphor, “Day star, son of the Dawn,” as “Lucifer,” and over the centuries a metamorphosis took place. Lucifer the morning star became a disobedient angel, cast out of heaven to rule eternally in hell. Theologians, writers, and poets interwove the myth with the doctrine of the Fall, and in Christian tradition Lucifer is now the same as Satan, the Devil, and — ironically — the Prince of Darkness.
Read more at : http://www.lds-mormon.com/lucifer.shtml