Why "Lord of the Rings"?

[Gordis]

I can't believe there is no such thread yet.
Maybe there is, but I failed to find it. In this case, sorry.

Now, simple question, why the Book is called "the Lord of the Rings"?

Who is the Lord of the Rings? Sauron, right. There is a quote about it:

LOTR, Many Meetings:
`Hurray!' cried Pippin, springing up. `Here is our noble cousin! Make way for Frodo, Lord of the Ring!'
'Hush!' said Gandalf from the shadows at the back of the porch. `Evil things do not come into this valley; but all the same we should not name them. The Lord of the Ring is not Frodo, but the master of the Dark Tower of Mordor, whose power is again stretching out over the world! We are sitting in a fortress. Outside it is getting dark.'

Now, imagine Tolkien calling his book "Sauron"?!

So, perhaps, the Lord of the Rings was Frodo, after all...

Thoughts?