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.
Ohtar is a Tolkien character. He is a character in "The Disaster of the Gladden Fields."
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