From what I know, in Simple Present, all verbs are followed by -s/es if the subject is a third-singular person. Such as makes, matches, buys, and studies.
I also know that if the verb is have, it becomes has if the subject is a third-singular person. And I'm wondering why it doesn't simply become haves, just like other verbs.
She has a book.
Why not: She haves a book.
So, my question is, what is the origin of the use of the verb has? I'm guessing euphony has something to do with it, but I need to support my guess.