Why do people still say lucifer is another name for satan?

lucifer was mentioned only one time in the bible, it was in Isaiah 12:14 and it was referring to a fallen Babylonian king....the word lucifer is a latin word and latin was not even a spoken language when Isaiah was written....lucifer means the morning star or bearer of light.....the bible does not state anywhere that lucifer is satan....(or is this another example of reading in between the lines so people can make up their own version)