This definition is from the OED online dictionary. This definition of the word is rarely used in our language today.

     2. The fact or quality of being authoritative or duly authorized; authority

This definition is not one that we usually use in our common language today. We do not think that being authentic would be having authority. What if we took the view of seeing leaders that were authoritative and that is what made them authentic? Such as Adolf Hitler, he was one of the most authoritative leaders of the world. It was because of his authenticity that made him such and impact on millions of people, even tho it was not for their well being.