Medici's name sake seems to come from an historically important Italian lineage:

(Also, they originated from the Mugello region. Very on-the-nose.)

Panau shares a name with a genus of moth, but more significantly it's one letter off from another Pacific Island not too far from Asia...

I couldn't find anything about San Espirito that wasn't about JC. Though, the island is very clearly inspired by Panama, where the U.S. toppled a dictator for their own personal gain. And what was the name of that operation? Operation Just Cause. (Also note, this would have been much more topical in 2006 when Just Cause was released. It would have been about as thought about as the Iraq war is to us now)

San Esperito maybe is Espírito Santo (Portuguese: [(i)sˈpiɾitu ˈsɐ̃tu] ⓘ; lit. 'Holy Spirit') is a state in southeastern Brazil.