The word Bible comes from the latin biblia.
It refers to a collection of books rather than just one book. That’s what The Bible is; a collection of books written by various authors over hundreds of years.
Biblia is the root of such words as bibliography in English or biblioteca, the Spanish word for library.
Check out the Online Entymology Dictionary for a nice long history of the word biblia taking us right back to the Greek word for Egyptian papyrus and the town from which it was exported.
According to a PBS program on The Bible Ta Biblia was used to refer to the Greek version of the Jewish scriptures (The Septuagint) centuries before Christ.
As for the Christian Bible it was being used as early as 223 AD.