Lucifer was originally a Latin word meaning "light-bearer" (from lux, "light", and ferre, "to bear, bring"), a Roman astrological term for the "Morning Star", the planet Venus.
"I will put enmity between you and the woman, and between your offspring and her offspring; he shall bruise your head, and you shall bruise his heel."
—Genesis 3:15 ESV
According to David J. Stewart
The reason Lucifer has been understood to be a proper name of the Devil has to do with the Latin translation of the Hebrew term Helel. This word was understood, by some, to be a proper name for the king of Babylon. It means "light bearer," or Lucifero in Latin. The Latin title became a popular name for this evil figure. When the King James translators rendered the Hebrew term into English, they kept the popular term "Lucifer" for the Devil.The word Lucifer was the direct translation of the Greek eosphorus ("dawn-bearer"; cf. Greek phosphorus, "light-bearer") used by Jerome in the Vulgate. In that passage, Isaiah 14:12, it referred to one of the popular honorific titles of a Babylonian king; however, later interpretations of the text, and the influence of embellishments in works such as Dante's The Divine Comedy and John Milton's Paradise Lost, led to the common idea that Lucifer was a poetic appellation of Satan.
A classic Roman use of "Lucifer" appears in Virgil's Georgics (III, 324-5):
"Luciferi primo cum sidere frigida rura carpamus, dum mane novum, dum gramina canent"
"Let us hasten, when first the Morning Star appears, To the cool pastures, while the day is new, while the grass is dewy"