What a rich and choice-laden language we speak.
Some common expressions have quite literal explanations. “Steal my thunder” came from English playwright John Dennis in the early 1700s. Dennis invented a machine to mimic the sound of thunder for his play Appius and Virginia. The play was a flop and things really turned to custard when, soon after, Dennis attended a performance of Macbeth.
He was extremely offended when he heard his thunder technique being used without his permission. “The villains will play my thunder but not my plays,” he is reported to have shouted, rather angrily.
“Caught between a rock and a hard place” also has a rather literal explanation. It comes from an Arizona miners’ strike in the early 1900s. The miners were caught between a rock (their job in a mine) and a hard place (the financial losses and hardships of striking).
During times of Middle East unrest, I have also heard the clever variant “between Iraq and a hard place”.
According to one source, “acid test” also comes from mining, or at least prospecting. Nitric acid was used to test whether gold was real or fool’s gold. The term has, however, moved with the times. In the psychedelic 60s it became slang for LSD (acid) experiments and later it was used in web development to check browser compliance standards.
“Let the cat out of the bag” is commonly believed to have come from medieval markets where disreputable sellers might replace the squirming piglet which was supposed to be in the bag with a common cat. Neither cats nor piglets are required today, the phrase simply means the accidental spilling of a secret.
When we turn a blind eye to something we owe a debt to British Admiral Horatio Nelson who was blind in one eye. He famously ignored a signal to withdraw during a battle in 1801. Lifting his spyglass to his blind eye he declared he could not see the order. No, things did not turn to custard, he subsequently led his men to victory.
“Mad as a hatter” is commonly attributed to Alice in Wonderland but has its origin in 18th century England. Hat makers of the time used mercury to treat the felt they used. Prolonged exposure to mercury often caused erratic behaviour, even tremors and hallucinations. Nowadays we just use the expression to refer to eccentricity and no mercury is required.
“To pull out all the stops” is commonly used to mean giving something your all, going all out. My research suggests this originally referred to the mechanics of a pipe organ; each stop on the organ controls airflow to the pipes so pulling out all the stops would achieve the fullest sound possible.
“Close, but no cigar” comes from 19th century fairgrounds. Possibly because worthless soft toys had not yet been invented, cigars were given as prizes for achieving success in fairground games such as the coconut shy and quoits. Today we use it to mean almost successful but not quite making it.
“Yeah, nah” is a tough one because it has no logical explanation.
Linguists have not even come close to earning a cigar by explaining it. Perhaps it is evidence that our use of language might be turning to custard.