Clams & Mirages
I recently came across the word 蜃気楼:, which means "mirage". The individual characters are a little strange, though - the first is given by the dictionary as "clam" while the last is "multi-story building". According to the Japanese Wikipedia article on mirages the etymology of the word lies in a Chinese myth of a kind of clam whose breath created illusory cities. There's even an illustration:
That is a bit strange.
It turns out the 蜃 character is never used to refer to a normal clam; in fact, it doesn't appear in any word except "mirage" in the dictionary I was using. It specifically refers to a mythical creature sometimes described as an ocean dragon, sometimes as a giant clam. English Wikipedia has an extensive article on the subject.
This antiquities seller has an ivory carving that looks like a city from one side and a row of clams from the other:
I can't find a decent shot of it, but a giant mirage-producing clam appears to have shown up in the Naruto anime and manga as well.
The English word "mirage", by comparion, probably comes via French, and ultimately from the Latin mirus, "wonderful", which is also the root of "mirror" and "miracle". Ψ