The problem with the biblical quote is "Lucifer" is Latin and it is not a proper name. It was a Latin reference to Venus (the "day star"). I am not sure if it was meant as a proper name for Satan by the KJV translators. If so it is an error.
In a sermon, KJV translator Lancelot Andrewes referred to "St Peter's
Lucifer in cordibus [daystar in your hearts]" (Hewison,
Selected Writings, p. 112). An edition of the Latin Vulgate printed with the 1538 Coverdale’s English translation of its New Testament has “
lucifer oriator in cordib” in its Latin text at 2 Peter 1:19 with its rendering in English as “the day star arise in your hearts”. Lancelot Andrewes evidently cited or used the Latin Vulgate’s word
Lucifer in his sermon with the meaning “daystar.” Daystar is Old English for morning star.
What did the KJV translators themselves mean by the choice of the word "Lucifer" in Isaiah 14:12? The 1611 KJV gives in its margin the literal meaning or acceptable alternative translation for "Lucifer" as "daystar." The KJV translators were clearly aware of the marginal note in the Geneva Bible, and they would have recognized that their marginal note at this verse would have associated this meaning “daystar” or “morning star” with this rendering “Lucifer.“
At the end of Isaiah 14, the 1549 edition of Matthew’s Bible has some notes that include these words: “Lucifer, the morning star, which he calleth the child of the morning, because it appeared only in the morning.” The marginal note in the 1560 and 1599 editions of the Geneva Bible for this word included the following: "for the morning star that goeth before the sun is called Lucifer." These two notes from two pre-1611 English Bibles that are on the KJV-only view’s line of good Bibles provide clear credible evidence concerning the meaning of the word "Lucifer" in English in the 1500's. The 1657 English translation of the 1637
Dutch States-General Version and
Dutch Annotations also indicated this meaning with its rendering "O morning-star" at Isaiah 14:12.
Since the 1611 edition of the KJV has several words capitalized that are not proper names, it is hard to know whether the KJV translators meant it to be a proper name or not. Beginning with the 1629 standard Cambridge KJV edition, several KJV editions have it not capitalized, but then the 1769 Oxford returned to capitalizing it.
Isaiah 14:12 [o Lucifer--1560 Geneva] [capitalization]
O lucifer (1675, 1679, 1681, 1709, 1715, 1720, 1737, 1743, 1747, 1754, 1764, 1765, 1768 Oxford) [1629, 1635, 1637, 1638, 1683, 1743, 1747, 1756, 1760, 1761, 1762, 1765, 1767, 1768, 1783 Cambridge] {1672, 1689, 1703, 1706, 1711, 1712, 1730, 1735, 1741, 1743, 1747, 1750, 1760, 1764, 1767, 1768, 1795 London} (1755 Oxon) (1722, 1751, 1760, 1769 Edinburgh) (1722, 1743, 1762 Dublin) (1645 Dutch) (1746 Leipzig) (1774 Bristol) (1782 Aitken) (1790 MH)
O Lucifer (1749,
1769 Oxford, SRB) [
1769 Cambridge, DKJB] {1611 London}