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!”
The first problem is that Lucifer is a Latin name. So how did it find its way into a Hebrew manuscript, written before there was a Roman language? To find the answer, I consulted a scholar at the library of the Hebrew Union College in Cincinnati. What Hebrew name, I asked, was Satan given in this chapter of Isaiah, which describes the angel who fell to become the ruler of hell? Please, I asked, explain this to me in a manner that I can understand and then explain to anyone, not just folks who have completed a degree either traditionally or through an online university.
The answer was a surprise. I had to sit back into a chair and take a moment before continuing. 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 Saint 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.
So “Lucifer” is nothing more than an ancient Latin name for the morning star, the bringer of light. That can be confusing for Christians who identify Christ himself as the morning star, a term used as a central theme in many Christian sermons. Jesus refers to himself as the morning star in Revelation 22:16: “I Jesus have sent mine angel to testify unto you these things in the churches. I am the root and the offspring of David, and the bright and morning star.”
And so there are those who do not read beyond the King James version of the Bible, who say ‘Lucifer is Satan: so says the Word of God’….”
Henry Neufeld (a Christian who comments on Biblical sticky issues) went on to say,
“this passage is often related to Satan, and a similar thought is expressed in Luke 10:18 by Jesus, that was not its first meaning. It’s primary meaning is given in Isaiah 14:4 which says that when Israel is restored they will “take up this taunt against the king of Babylon . . .” Verse 12 is a part of this taunt song. This passage refers first to the fall of that earthly king…
How does the confusion in translating this verse arise? The Hebrew of this passage reads: “heleyl, ben shachar” which can be literally translated “shining one, son of dawn.” This phrase means, again literally, the planet Venus when it appears as a morning star. In the Septuagint, a 3rd century BC translation of the Hebrew scriptures into Greek, it is translated as “heosphoros” which also means Venus as a morning star.
How did the translation “lucifer” arise? This word comes from Jerome’s Latin Vulgate. Was Jerome in error? Not at all. In Latin at the time, “lucifer” actually meant Venus as a morning star. Isaiah is using this metaphor for a bright light, though not the greatest light to illustrate the apparent power of the Babylonian king which then faded.”
Taken from: https://www.lds-mormon.com/lucifer.shtml