Where do the terms “Old Testament” and “New Testament” come from? What do they mean? Is it right for us to name the two divisions of our Bible this way?
Melito of Sardis is widely regarded as the person who coined the terms “Old Testament” and “New Testament”. His is the earliest known canon (list of books) of the Old Testament (circa 180 CE). But I discovered recently that the New Testament itself spoke of the Old and New Testaments a century before Melito.
In 2 Corinthians 3:14, Paul refers to the “old covenant” as a written document (“when they read the old covenant”). It’s important to explain here that the word for “covenant” in this passage is the Greek διαθήκη (diathēkē), which variously means “testament” or “covenant”. Look at this same passage in the King James and you’ll find the word “testament” there in place of “covenant”. When Melito of Sardis coined the terms, he was writing in Greek and used exactly this word διαθήκη.
What’s remarkable is that just 8 verses back, in 2 Corinthians 3:6, Paul states that God has made him and the other apostles “ministers of a new covenant” (same word διαθήκη, and if you look at the KJV you’ll find “new testament” here). It’s hard to escape the implication that Paul knew he was contributing to a new collection of Scripture which he would at least informally have referred to as the “new covenant” just as he referred to the Jewish Scriptures as the “old covenant”.
It’s impossible to know for certain if this is where Melito got his terms for the Old and New Testaments, but I think it’s a remarkable coincidence if not. I think perhaps it would be better for us to call them the Old and New Covenants, but Testament is a valid translation of διαθήκη and it’s rather late to change our conventional English wording now. Whether we call them Covenants or Testaments, though, I see 2 Corinthians 3:6, 14 as a solid biblical basis for naming our two collections of Scripture as we do.