Lucifer is a Latin word derived from two words, lux ('light), and fero ("to bear,bring"), and means "light-bearer, light-bringer". In Roman mythology, Lucifer was a deity equivalent to the Greek Heosphorus, and the planet Venus was known by the name Lucifer in Roman astrology before being given its current name. In Christianity, Lucifer has become synonymous with Satan or the Devil, despite the original Judaic mythology considering Lucifer and Satan to be two quite separate entities.
Lucifer is mentioned in only one place in the Bible (Isaiah 14:12), in translations based on the Latin translation largely made by St. Jerome in the fourth century. The Hebraic texts refer to Heylel Ben-Shachar (הילל בן שחר)where 'Heylel' is the Hebrew word for the planet Venus, and Ben-shachar means "son of the dawn." Isaiah 14 starts out discussing the King of Babylon, and the reference "morning star, son of the dawn" originally meant specifically that king. Then St. Jerome translated Heylel into Lucifer. Much of Christian tradition also draws on Revelation 12:5 ("He was thrown down, that ancient serpent") in equating Lucifer, Satan, and the serpent in the Garden of Eden.
Lucifer is a key protagonist in John Milton's Protestant Christian epic, Paradise Lost. Milton presents Lucifer almost sympathetically, an ambitious and prideful angel who defies God and wages war on heaven, only to be defeated and cast down. Lucifer must then employ his rhetorical ability to organize hell; he is aided by Mammon and Beelzebub. Later, Lucifer enters the Garden of Eden, where he successfully tempts Eve, wife of Adam, to eat fruit from the Tree of knowledge of good and evil.
Lucifer is a deity in the Voodoo religions.
Lucifer was the name of a research block cipher developed at IBM by Horst Feistel and his colleagues in the 1970's. It had a 128-bit key but only a 32-bit block size, and was vulnerable to cryptanalysis. It was a forerunner of DES, the US federal data encryption standard.