Would you happen to know why we call Japan 'Japan' and not Nihon or Nippon?This is one that I dug up a long time ago because I wondered the same thing.
The kanji for "Japan" are 日本. They respectively mean "sun" and "origin", or together "origin of the sun". This is of course from the perspective of China, to the East of which Japan lies in the same direction as where the sun rises. That's also where English gets "land of the rising sun" from, which is simply a more nuanced translation of the characters than "origin of the sun".
The word in Japanese is pronounced Nihon or, with a bit more emphasis or formality, Nippon. Nihon is actually a relatively recent shortening of Nippon, which in turn is a shortening of the readings of the two characters following normal character combination rules. 日 can be read nichi or jitsu in this case, and nichi is preferred here, while 本 can be read as hon. Typically, when two character are adjacent to each other in a single word, the first ends in chi or tsu, and the second starts with h-, the chi or tsu is dropped, the consonant doubled (or っ is added for all of you who are beyond romaji), and the h- becomes a p-. You thus get Nippon. You can also see the pattern in, e.g., ippon (一本, いっぽん, "one long, slender object") combining ichi and hon, or in happyaku (八百, はっぴゃく, "eight hundred") combining hachi and hyaku.
Once I had figured all this out when I was first studying Japanese, I thought I had figured out where "Japan" came from as well; obviously people had just used the other reading for 日 at some point, i.e., jitsu, which would have resulted in a reading of Jippon, and that's only a linguistic hop, skip and a jump away from "Japan".
As it turned out, I was on the right track but not quite there.
Nihon and "Japan" ultimately share the same etymological roots, but the path to the English word isn't very clear. It's believed that it came to English via one of the Chinese dialects' pronunciation of the characters 日本. It's these same pronunciations that likely supplied both the j in jitsu, and in "Japan", so my guess was a wee bit too high in the etymological tree.
Marco Polo called Japan "Cipangu", which, in Italian, would be pronounced like "Cheepangoo". (The gu is from the Chinese character 国, meaning country or kingdom, and which is currently pronounced guó in Mandarin.) This is thought to have come from a Wu dialect like Shanghainese. The Portuguese also brought words like Giapan over to Europe, which ultimately led to the English word. Below are a few of the Chinese dialects that might have been involved and their modern day pronunciations of Japan:
Names of Japan on Wikipedia
Japan in the Online Etymology Dictionary