What is the "original" word of God?

Everything I know about Christianity and Jesus is based on the "original" word of God. But I am having trouble understanding what is meant by "original". For example, Paul's source for his scripture is divine revelation only. So God's supernatural word was transmitted to Paul's brain and stored as a memory. Are those memories in Paul's brain the "original" word of God? Unfortunately the human brain can forget things, so perhaps it would be better to call the first words that Paul wrote down the "original" word of God. However it bothers me to move further from the source of the "original" word because Paul may not have transcribed it accurately. As a different example, Luke uses for his gospel Mark and the writings of Flavius Josephus as sources, and possibly another unknown source Q. Suppose that tomorrow we find the Q source, and it just so happens to be everything in Luke that is not contained in Mark or the writings of Flavius Josephus. In this case Luke is simply an anthology, so what would we say the "original" word of God is with respect to Luke?