no japan is the mystery english name i think.
as much as i hate to reference a yahoo answers source, this is what i found after a quick google:
The origin of the word "Japan" used in western languages is less clear. One theory holds that it came from the Portuguese "jipang", which in turn was an attempt to pronounce "Jihpenkuo", the name for Japan used in northern China. Another idea is that Dutch traders pronounced "Yatpun", the name used in southern China, as "Japan" (the 'j' being pronounced like a 'y').
Yet more info:
As mentioned above, the English word "Japan" has a circuitous derivation; but linguists believe it derives in part from the Portuguese recording of the early Mandarin Chinese or Wu Chinese word for Japan: Cipangu (日本国), which is rendered in pinyin as Rìběnguó, and literally translates to "country of sun origin". Guó is Chinese for "realm" or "kingdom", so it could alternatively be rendered as "Japan-guó".
Cipangu was first mentioned in Europe in the accounts of the travels of Marco Polo. It appears for the first time on a European map with the Fra Mauro map in 1457, although it appears much earlier on Chinese and Korean maps such as the Kangnido. Following the accounts of Marco Polo, Cipangu was thought to be fabulously rich in silver and gold, which in Medieval times was largely correct, owing to the volcanism of the islands and the possibility to access precious ores without resorting to (unavailable) deep-mining technologies.
The modern Shanghainese pronunciation of Japan is Zeppen [zəʔpən]. In modern Japanese, Cipangu is transliterated as ジパング which in turn can be transliterated into English as Jipangu, Zipangu, Jipang, or Zipang. Jipangu (ジパング) as an obfuscated name for Japan has recently come into vogue for Japanese films, animes, video games, etc.
Source(s):
from here:
Yahoo! Canada Answers - Why is japan called japan?
perhaps someone with more knowledge could confirm?