One of the quirkier examples is Holland/the Netherlands. From what I can tell they are synonymous in English. I can't think of another country with two names in English

Many of my Dutch friends get annoyed by English speaking people using the name of a province for the name of the country. There is a North Holland and a South Holland, and both are part of the Netherlands. With so many Dutch people here,it has become easy to get into the habit of callign the country by its proper name, and it helps that the people call their language Nederlands. Dutch comes from "Deutsch" I seem to recall reading somewhere.