The Boston Tea Party, is that an idiom?
No. You apparently didn't learn a lot about American history when you lived here, because the Boston Tea Party was one of the seminal events leading up to the American Revolution.
Tea was a valuable commodity in the late 18th century, and the only way the American colonists could obtain it was from British merchant ships because Britain had a monopoly on trade with its colonies. King George taxed tea heavily, more heavily than it was taxed in England. The American colonists were not represented in Parliament, so they had no voice in the setting of tax rates. "Taxation without representation is tyranny," coined by Rev. Jonathan Mayhew in a sermon in Boston in 1850, summed up the principal grievance that the colonists had with the Crown, and this slogan became the rallying cry for the Revolution.
In 1773, a mob of Americans, poorly disguised as Indians to avoid identification, stormed a merchant ship and tossed all of its tea into Boston Harbor, in protest of the unfair taxation. This was called the Boston Tea Party and it is one of the most iconic events in our nation's history.
"Let them eat cake" is that an idiom?
This time it's French history so you're excused.
Marie Antoinette was the Queen of France when the French Revolution started. I would have said, "had the misfortune to be queen at that time," but her inept and downright mean-spirited leadership was one of the things the citizens revolted against. The country's economy was completely dysfunctional. One day one of her advisors ran into her court and said tearfully, "There is no bread in any of the bakeries! Your people are starving!" In reply, she uttered the words that have become the symbol of that country's revolutionary era: "Let them eat cake!" She was executed by guillotine in 1793.
The American Revolution was civil, polite and honorably waged compared to the French Revolution. It left so much rancor and ill will--not to mention a government that wasn't a whole lot more competent than its royal predecessor--that Napoleon was soon able to seize power and turn it away from democracy.
The Radical Republican Right calls their meetings "tea parties" to evoke the anger of the Boston Tea Party. They fraudulently imply that President Obama is as much of a tyrant as King George I, even though he was elected democratically by a majority of their countrymen and almost any "tyrannical" decision he makes can be thwarted by Congress or the Supreme Court under the rules of the Constitution. (Hey, I'm not the guy's biggest fan but I understand how our govermment works, and when I don't like what they do I blame the people who elected them.)
So the people who attend these "tea parties," or who support them in spirit, call themselves "teabaggers," an obvious and disarmingly cute derivation.
Most jargon, slang, aphorism, idiom contradicts the principle of compositionality.
Well duh. No one promised that language would be logical. Even the normal evolution of language violates compositionality: for the very good reason that many "proper" words and phrases evolved from idioms. Apparently that's how people think.
Finally, is there a reason so many idioms/expressions are related to food?
Your leading examples don't support that assertion. The Boston Tea Party really was about tea, and Marie Antoinette's remark really was about cake.
But even if your assertion is correct, it's hardly remarkable. Food is a high priority in our lives, and it's something all cultures in all eras have in common.
Do you know the etymology of the word "companion"? It's someone you share your
bread with. Latin
panis. (Whence French
pain, Italian
pane, Spanish
pan, etc.)
