Japan is an exonym. In Japanese Nihon or Nippon.
[History]
In earlier times, my country's name was Yamato or Oyamato, because the government was located in Yamato region, western Japan.
About the sixth century, the name Nihon and Nippon began to be used. Nihon or Nippon originally means the far eastern country where the sun rises first.
In 1299 Marco Polo first introduced Japan to Europe as Zipangu in his book Books of the Marvels of the World. It is said that Marco Polo heard the pronunciation of Nihon Koku or Nippon Koku (Koku means nation) in language of Beijing as Zipangu. That's the origin of an exonym Japan.
[Which is correct: Nihon or Nippon?]
So, which is correct, Nihon or Nippon? The answer is both are correct. There are no legal bases for name of the country in Japan. Both are commonly used. But externally, Nippon was usually used. In compound word, Nihon is likely to be used (e.g. Nihon go).
[Usage of Nihon]
Nihon go (Japanese)
Nihon Kai (the Sea of Japan)
Nihon shu (Sake)
[Usage of Nippon]
Nippon ichi (number one in Japan)
Gabmare Nippon! (Go, Japan!)
Dai Nippon Teikoku (Empire of Japan)
[Cases both Nihon and Nippon are OK]
Nihon jin or Nippon jin (Japanese people)
Nihon Koku Kenpou or Nippon Koku Kepou (The Japanese Constitution)
Nihon Rettou or Nippon Rettou (the Japanese Archipelago)
Nihon Ginko or Nippon Ginko (Bank of Japan) *
* A phrase "Nippon Ginko" is printed on Banknotes of the Japanese yen. So, clerks of the BOJ tend to say Nippon Ginko. But many Japanese people also commonly say "Nihon Ginko." Bank of Japan Act doesn't state which is correct.
