The word "satan" is actually Hebrew, and literally means "adversary", though "opposer/opponent" is as good a synonym as any. It is used in context in the hebrew Torah to describe an adversary (7 times), and as the specific Adversary against God, Satan (19 times).
It was translated into Latin also as Satan, but in Greek it was translated as "diabolos", which is the root of our english name The Devil. As Cancer pointed out, "Lucifer" appears only once, in Isaiah 14:12. It is obvious, when we are talking about Yahweh/Elohim/God's opponent, Satan is his name.
How did we come to associate Lucifer with Satan, then? This is thanks to a Latin misinterpretation of the Hebrew term from Isaiah 14:12, "heylel ben shachar", which literally means, "the most-praised son of the morning".
Heylel is actually an adjective, which means "highly-prized" in Hebrew. It comes from the verb "halal", to praise, and is the root of another common word of praise, Halelujah. This word also takes on the connotations of the dark side of pride, as well, specifically the boastful arrogant nature of pride, which is what makes it one of the seven deadly sins.
In fact, this is plain to see in the next verse, as we see how this "heylel ben shachar" claimed he would ascend into heaven above and exalt himself higher even than God. It isn't said by name, nor even suggested by reference, such as a serpent or dragon, but merely implied that this boastful would-be king is Satan.
When St. Jerome was translating the various versions of the Bible into one consolidated canon, known as the Latin Vulgate, he chose to use a different interpretation of "most-praised", that being, "shining", or "the brightest". This would now read as "the brightest shining son of the morning", and he chose the word "lucifer", the Latin term for "light-bearer", for this person.
This may or may not have been influenced by the fact that Lucifer was the name of the Roman god associated with the planet we know as Venus. Venus is so bright in the heavens that it can be seen day and night, giving it the other nickname, the morning star. Funny how this nickname, derived from the Greek god Phosphorus for the same planet, is commonly used to reference Jesus Christ.
Thanks to this association, Isaiah 14:11-15 now reads as follows (in King James Version - your mileage may vary):
Isa 14:11 Thy pomp is brought down to the grave, [and] the noise of thy viols: the worm is spread under thee, and the worms cover thee.
Isa 14:12 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!
Isa 14:13 For thou hast said in thine heart, I will ascend into heaven, I will exalt my throne above the stars of God: I will sit also upon the mount of the congregation, in the sides of the north:
Isa 14:14 I will ascend above the heights of the clouds; I will be like the most High.
Isa 14:15 Yet thou shalt be brought down to hell, to the sides of the pit.
The rest, boys and girls, is history, and left to fester therein.
Rev. Daniel
"Pick one, pick none, pick all of the above!"
