That would be an ogre (although ogres are not specifically an invention of Tolkien). Actually, orc would be a better answer. Tolkien's fiction included both ogres and orcs, but the orcs were his invention, unlike the ogres.
The Tolkien creature beginning with the letter "O" is an "Orc." Orcs are fictional humanoid creatures in J.R.R. Tolkien's Middle-earth legendarium, serving as soldiers and minions of dark lords like Sauron. They are often depicted as fierce, brutal warriors.
orc
Tolkien's monster starting with the letter "O" is the Orcs, who are a race of twisted creatures bred by the dark lord Sauron in the world of Middle-earth.
Orc, Olog-hai
A herb beginning with the letter "o" is oregano.
octopus
Feline mammal of south America beginning with the letter O is an "ocelot."
Some names beginning with the letter O are:OlafOleanderOliveOliverOllieOmarOpalOpheliaOprahOrvilleOscarOtto
· Ornithomimus · Ouranosaurus
optometrist
Ontario
Oman
No there is not
oasis