The two books of Kings originally formed one book only in the Hebrew Bible. The translators of the Septuagint introduced the separation into two books and this separation was made also in the Vulgate. In the Hebrew manuscripts of the OT the division into two books first appeared in the 15th century. It was first used in a Hebrew print of the Bible by Daniel Bomberg. The two books of Kings are called the 3rd and 4th book of Kings in the Septuagint as well as the Vulgate.