While there may have been people living on the island at different times during its history before discovery by the Portuguese, there is no evidence for this. Nevertheless the Portuguese discovered the island for themselves and the trade networks connected to the Kingdom of Portugal on New Year’s Day in 1473.
In Portuguese, New Year’s Day is Dia do Ano Bom, and it was for this day that the discoverers named the island. You can see how the present name of Annobón is derived from Dia do Ano Bom, especially in consideration of subsequent Spanish influence on the development of the island.
Today, Annobón is part of the independent state of Equatorial Guinea. Interestingly, during the final years of the Francisco Macías Nguema administration of Equatorial Guinea, the island was called alternatively Pigalu or Pagalu, from the Portuguese word for “parrot” (papagaio).