Butterflyblue has a great post on Japanese family names. Did you know (to take one startling fact) that Japan has
more such a large number of different surnames than any other country in the world (about 120,000)? I’ll let you discover various piquant examples in situ, but I can’t resist quoting the final paragraph:
Yes, in the Heian period and after, it was common to use “Kuso” ['shit' -- LH] in names, which means just what you think it means. The famous poet “Kinotsurayuki,” who wrote the Tosa Diaries, is a notable example. His birth name was “Ako Kuso,” which means “my child…shit.” Amazing that a man with this kind of name grew up to be successful in life. Nor is he an isolated case. Names like “Kusoko” and “Oguso” were in vogue among the nobility. The book explains that this has to do with the belief in the god of the toilet. Since the toilet god keeps you healthy, it stands to reason he would be helpful in rearing a healthy child. This seems very out of place in the Japan of today, but it persists in a small way in the superstition that a pregnant woman should keep her bathroom clean if she wants to have a beautiful baby.
Addendum. Mark Liberman points out in the comments, and in more detail in this Language Log post, that the U.S. has far more surnames. Of course, in a sense it’s an unfair comparison, because the U.S. has surnames from just about every ethnic/linguistic group in the world, but butterflyblue’s statement is clearly incorrect as it stands.