The Old Testament and the New Testament.
Etymology
Latin testamentum -> Greek diatheke, meaning "covenant" in most biblical occurrences. The terms Old Testament and New Testament came into general Christian use in the late 2nd century. Tertullian was one of the first to call the Christian Scriptures the "New Testament. He rendered diatheke as instrumentum (a legal document) and by testamentum, though only Testament has survived.
The first appearance was in a composition against Montanism by an unknown author in circa A.D. 190.
(The Origin of the Bible: Newly Updated by F. F. Bruce, J. I. Packer, Philip W. Comfort, and Carl F. H. Henry, 2020. Biblical Languages by Larry Walker. Section One: The Authority and Inspiration of the Bible. Page 5, 66)