Tempest in a teapot
A small or unimportant event that is over-reacted to, as if it were of considerably more consequence.
Readers from England who get irate that 'a tempest in a teapot' is a mangling of their perfectly good phrase 'a storm in a teacup' and that this US interloper only exists because of the neat alliteration of tempest and teapot need to calm down; the tempest version is the earlier form and it isn't American in origin.
In fact, neither the teacup nor the teapot were the first location of the said storm. As we will see, the phrase is really 'bad weather in a domestic receptacle of your choice'.
The expression probably derives from the writing of Cicero, in De Legibus, circa 52BC. The translation of his "Excitabat fluctus in simpulo" is often given as "He was stirring up billows in a ladle". Other cultures have versions of the phrase in their own languages. The translation of the Netherlands version is 'a storm in a glass of water', and the Hungarian 'a tempest in a potty'.
The first user of the expression in English made no mention of tea-making, although he wasn't far away. The Duke of Ormond's letters to the Earl of Arlington, 1678, include this:
"Our skirmish ... is but a storm in a cream bowl."
Also, before the 'teacup/teapot' versions were well-established, another nobleman came up with a version that didn't involve the tea-table at all. The Gentleman's Magazine, 1830, records:
"Each campaign, compared with those of Europe, has been only, in Lord Thurlow's phrase, a storm in a wash-hand basin."
'Tempest in a teapot' is the version that is used most often in the USA but which nevertheless appears to have a Scottish rather than an American origin. Blackwood's Edinburgh Magazine, 1825, included this:
What is the 'tempest raging o'er the realms of ice'? A tempest in a teapot!
Finally, we come to the 'storm in a teacup' version of the phrase that we English might imagine is the 'proper' original version. This appears to be neither original nor English as it is later than the versions above, and the first mention that I can find of it also hails from north of the border. The Scottish novelist Catherine Sinclair wrote a novel of fashionable society life, Modern Accomplishments, or the march of intellect, in 1838:
"As for your father's good-humoured jests being ever taken up as a serious affair, it really is like raising a storm in a teacup."