My favorite is the Swedish word gökotta: "to go out early in the morning, traditionally on Ascension day, to listen to the birds of spring, especially the cuckoo."

Regarding this topic, see http://en.wikipedia.org/wiki/Ilunga which says "When asked for confirmation by one reporter, representatives of the Congo government recognized the word only as a personal name." and see the commentary at Language Log at http://itre.cis.upenn.edu/~myl/languagelog/archives/001104.html .