Gandalf mentions them in the books but refuses to give further explanation
“There are many evil and unfriendly things in the world that have little love for those that go on two legs, and yet are not in league with Sauron, but have purposes of their own. Some have been in this world longer than he.” - Fellowship of the Ring
"Far, far below the deepest delving of the Dwarves, the world is gnawed by nameless things. Even Sauron knows them not. They are older than he. Now I have walked there, but I will bring no report to darken the light of day." - Two Towers
What do you think these things are? GeekZone has a couple of theories in his video:
https://www.youtube.com/watch?v=lBjypmueZUI
Agree or disagree? Do you have your own theories about them?
There are also unnamed creatures in The Hobbit, who lived under the Misty Mountains.
http://tolkiengateway.net/wiki/Nameless_Things
I believe they are of the same nature as Ungoliant.
There's yet another possibility. These entities might have originated from altogether outside of the universe created by Eru Ilúvatar. They could be Outsiders akin to H.P. Lovecraft's Great Old Ones and Elder Gods. There are a number of creatures in Lovecraft's mythos that would feel right at home in the deep places of Middle-earth, such as: Chthonians; Deep Ones; Dholes; Formless Spawn; Gugs; Shoggoths; and Wamps.
I have heard the opinion that these unnamed things sound very Lovecraftian.
Yes, if only because we know so little about them!
The watcher in the water reminds me a lot of fan art depicting Cthulhu, one of Lovecraft's monsters.
Peter Jackson wasn't the only one who made the Watcher look like a Kraken. The MERP game actually lists the Watcher as one. Maybe Jackson took his cue from the game.
On that note, perhaps some of the weirder D&D monsters can be explained as such, although the characters would have to be quite powerful to take them on.