I believe it has been traditionally stated as "A tempest in a teapot", but the original may have actually involved "storm" and "saucepan". I believe it originates with the author Athenaeus (c. 200 AD) who said (in reference to an actual storm) something like "I have seen a more formidable storm in a boiling saucepan." It's been shortened up and alliterated (and much improved) since. I would cite an actual reference for this information, but I'm afraid it has been classified in the interest of national security (don't you remember 9/11 ?!?!).