I just reread LOTR after forty years away from it, so for an old guy I got the joke quickly. And I even know there were 19 other rings of power made, for the Elves, Dwarves, and Men.
"Three Rings for the Elven-kings under the sky,
Seven for the Dwarf-lords in their halls of stone,
Nine for Mortal Men doomed to die,
One for the Dark Lord on his dark throne
In the Land of Mordor where the Shadows lie.
One Ring to rule them all, One Ring to find them,
One Ring to bring them all, and in the darkness bind them,
In the Land of Mordor where the Shadows lie."
Gives you a nerdgasm, doesn't it?