Froschmausekrieg, or how not to impress your German friends

This afternoon I came across this post on Boing Boing about the German word Froschmausekrieg which mean war between frogs and mice.

When my German colleague stopped by my office later in the day, I proudly proclaimed, "Froschmausekrieg!". To which he said, "Eh? War between frogs and mice? What are you talking about?"

So I guess it is a real word, but it isn't a common idiom, which kind of defeats the purpose.