One Ring was the One Ring. Frodo inherited the Ring from his uncle Bilbo Baggins. In Tolkien's earlier novel, "The Hobbit", Bilbo found the Ring in the caverns beneath the Misty Mountains. It had been lost in the caverns by Gollum, who used the invisibility it conferred to hunt orcs to eat. Gollum, a hobbit previously known as Sméagol, had kept the Ring for hundreds of years. He had murdered his friend Déagol to get the Ring shortly after Déagol found it in the river Anduin. Many centuries earlier the Ring had betrayed Isildur and fallen from his finger into the Anduin
The Fellowship of the Ring the decision to publish "The Lord of the Rings" in three volumes was made, Tolkien had hoped to publish the novel in one volume, possibly also combined with "The Silmarillion". However, he had proposed titles for the individual six sections. Of the two books that comprise what became "The Fellowship of the Ring" the first was to be called "The First Journey" or "The Ring Sets Out". The name of the second was "The Journey of the Nine Companions" or "The Ring Goes South". The titles "The Ring Sets Out" and "The Ring Goes South" were used in the "Millennium