Fernando Poo

Fernando Poo, aka Bioko, is an island 32 km off the west coast of Africa, specifically Cameroon, in the Gulf of Guinea.

Historical
The island was named after Fernando Pook the first European to see the islands in the Gulf of Guinea around 1472. He was also known as Fernão do Pó, Fernão Pó, or Fernando Pó. He was a 15th-century Portuguese navigator and explorer of the West African coast. He named it Formosa Flora ('Beautiful Flower'), but in 1494 it was renamed by Europeans as Fernão do Pó.

Conspiratorial
Much of the action of The Illuminatus! Trilogy is centred around a coup d'etat on the island which is a trigger for nuclear war.

The Coup
The Coup of Fernando Poo is carried out, in 1973, by Captain Ernesto Tequilla y Mota who consults Edward N. Luttwak's Coup d'État: A Practical Handbook to do so.

Atlantis
The (fictional) anthropologist of the book, J.N Marsh, claims that certain artifacts found on Fernando Poo prove the existence of Atlantis.

Symbolism
In the book the name of the island is changed from Po to Poo, why this is is not certain, it could be down to a spelling error. The relevance of the original spelling would indicate that it should be kept as Po because the I-ching Po (23) is a significant symbolic part of the book, indicating the increasingly chaotic political circumstances of the plot, it could be that adding the extra 'o' brings attention to the significance of the word itself... however, it is most likely just toilet humor.