1. “Let the cat out of the bag.”
Meaning to reveal a secret, “letting the cat out of the bag” finds its roots in 18th-century street fraud. Suckling pigs were often sold in bags, and a popular scheme was to replace the pig with a cat and sell it to an unwitting victim.
2. “Don’t look a gift horse in the mouth.”
Horses’ gums recede with age, leading to longer teeth. A common way to inspect a horse’s “worth” is to check it’s mouth, hence the phrase. Receiving a horse as a gift and immediately inspecting its value was considered offensive, much like inquiring about the worth of a present today is rude.
3. “You’re pulling my leg.”
Meaning to tease someone or jokingly lie to them, “pulling one’s leg” actually has sinister origins, rooted in the criminal world of the 18th century. Street thieves would literally pull victims down by their leg in order to more easily rob them.
4. “Eating crow.”
To eat crow means to admit fault or be proved wrong after taking a strong position. The Bible lists crow as unfit for eating, and along with buzzards and rats, it was actually illegal to eat crow in the Middle Ages. As such, it was notably humiliating to consume.
5. “Break a leg.”
The term “break a leg” originates in theater. Since superstitions run rampant in the theater, it’s not surprising to learn that wishing someone good luck outright is actually considered bad luck. Instead, it was more suitable to wish ill will on someone before a performance, since the opposite was supposed to occur.
6. “Can’t hold a candle to…”
Before electricity, workers needed a second set of hands to hold a candle for them. Holding a candle was clearly a less challenging job, so someone who isn’t even qualified to provide light to a competent worker obviously wouldn’t be able to perform the task himself.
7. “Dressed to the nines.”
Meaning to dress exceptionally well, there’s no concrete consensus on the origin of “dressing to the nines,” but the most popular theory comes from the fact that the very best suits used a full nine yards of fabric.
8. “Don’t count your chickens before they’re hatched.”
The short answer is that Aesop said it. He wrote of a young milkmaid balancing a pail on her head. The girl thought, The milk in this pail will provide me with cream, which I will make into butter, which I will sell in the market, and buy a dozen eggs, which will hatch into chickens, which will lay more eggs, and soon I shall have a large poultry yard. I’ll sell some of the fowls and buy myself a handsome new gown and go to the fair, and when the young fellows try to make love to me, I’ll toss my head and pass them by. At that moment, the girl tossed her head and lost the pail of milk. Her mother admonished, “Do not count your chickens before they are hatched.”
Solid advice, mom.
9. “Crocodile tears.”
“Crying crocodile tears” means to fake being upset or force tears that are inauthentic. An ancient anecdote by Photios claimed that crocodiles weep in order to lure prey, which is most likely where the idiom comes from.
10. “Close, but no cigar.”
Carnivals used to give out cigars as prizes, so almost winning would get you close to achieving a cigar, but not quite. The phrase evolved in meaning and now refers to coming close to a goal but falling short.
11. “Once in a blue moon.”
A blue moon is the second full moon in a single calendar month, and it’s rare as heck. The phrase “once in a blue moon” is used colloquially to mean something that doesn’t happen very often.
12. “Mind your p’s and q’s.”
In the 17th century, pubs served beer in pints and quarts. If a patron was getting unruly, the bartender might warn them to mind their p’s and q’s. Now the term simply means to mind your manners, drunk or not.
13. “The kiss of death.”
“The kiss of death” marks the demise of something. Its roots rest in the Italian mafia, where someone who’s been marked for death receives the metaphorical kiss prior to execution.
14. “Rule of thumb.”
The “rule of thumb” as a form of rough measurement probably comes from carpenters approximating inches with their thumbs. Another theory is that farmers used the length of a thumb to estimate how deep to plant seeds.
15. “Sleep tight!”
Simply meaning to sleep well, the phrase “sleep tight” dates from the time when mattresses were supported by ropes. These ropes needed to be pulled tight to provide a stable mattress and a good night’s rest.
16. “A square meal.”
Nobody actually knows where this idiom came from, though the Royal Navy did serve meals on square plates at one point. Another idea is more linguistic in nature: the use of “square” to mean honest and straightforward goes back to at least the 16th century, which makes sense as “square meal” refers to a healthy, hearty dinner. This one might remain a mystery.
17. “Stay on the straight and narrow.”
Today it means to generally stay out of trouble, but the original phrase is actually biblical in origin. Matthew 7:13/14 described the gates to heaven as “strait” and the way to eternal life as “narrow.”
18. “Three sheets to the wind.”
Sailors had a lot of terms for being drunk and they all related to the ship. Being tipsy was “a sheet in the wind’s eye” and being hammered was a full “three sheets to the wind.” The sheets in question were actually the ropes that held down the sails, so if all three ropes were loose, the sails would billow about like a drunken sailor.
19. “White Elephant.”
Albino elephants were highly regarded in Southeast Asia, and they were cared for lavishly. The term “white elephant” eventually evolved to mean any valuable but burdensome possession of which its owner cannot dispose and whose cost of upkeep is out of proportion to its usefulness or worth.