It's a language like anyone elses. When koine Greek began to be restudied in western Europe, they noticed that it didnt look like classic Greek or 15th century Greek, so some scholars thought it was Holy Spirit Greek. Then they started studying non-Scriptural letters and scrolls such as a merchant's inventory and realized it was just another form of Greek. Mind you, no one ever bothers asking the Greeks how we read it........ sigh.
For a long time Koine Greek confused many scholars. It was significantly different from Classical Greek. Some hypothesized that it was a combination of Greek, Hebrew, and Aramaic. Others attempted to explain it as a "Holy Ghost language," meaning that God created a special language just for the Bible. But studies of Greek papyri found in Egypt over the past one hundred years have shown that this language was the language of the everyday people used in the writings of wills, private letters, receipts, shopping lists, etc. - Bill Mounce (author of Basics of Biblical Greek)
