What does the Japanese name for Japan actually mean?

Origin of the sun - Nihon or Nippon, written with characters meaning sun and origin. It is a description written from China looking east, which is where the sun rises from if you are standing in Chang'an, and Japan adopted it in the seventh century in correspondence with the Chinese court.

That correspondence includes one of the more pointed letters in diplomatic history. A Japanese envoy carried a message addressed from the sovereign of the land of the rising sun to the sovereign of the land of the setting sun - which the Chinese emperor is recorded as receiving with displeasure, since the implication was equality with, or a rising against a setting, the greatest power in the region.

The English name comes by a long detour. Japan reaches English through Portuguese from a Malay word from a southern Chinese pronunciation of the same characters, which is why it sounds nothing like what the country calls itself - the same pattern as Germany for Deutschland or Greece for Hellas. Nippon is the more formal reading and appears on stamps, currency and at sporting events; Nihon is what people say.