Polynesia is not one country. It is a name for a huge spread of islands in the central and southern Pacific Ocean. Hawaii, Tonga, Samoa, and the islands of French Polynesia (Tahiti is the famous one) sit in this group. The name was borrowed from French Polynésie, made up in 1756: poly- 'many' + a Greek word for 'island', so 'many islands'. At first the name was used more loosely for Pacific islands in general. Later, in 1832, another scholar set the narrower use we have now — this eastern group — and left Melanesia and Micronesia as the other two famous Pacific island names on the map. Though actually, those borders are a scholars' drawing, not a fence in the sea: people, languages, and boats have always crossed them. English keeps the capital P because it is a place name.