Ever wonder what your Achilles’ heel is?

Well, this story is not about heels. Instead, it’s about language, one of the greatest inventions of all time. Language is usually quite specific. If you ask a teacher who wrote the Declaration of Independence, it’s pretty clear what you want to know.

But suppose you told a classmate that math was your Achilles’ heel. Would she know what you were talking about? (Achilles is a character in “The Iliad” who was invincible except for one of his heels. If math is your Achilles’ heel, that implies it’s your weakest subject.)

Referring to math as your “Achilles’ heel” is an example of an idiom.

An idiom is a phrase whose meaning can’t be explained by looking at the words one at a time.

Idioms come from old customs, informal speech, folksy sayings, proverbs and works of literature. Like individual words, experts don’t always agree on how or when an idiom made its way into the language. Some idioms are recent, while others have been around for centuries. Here are some of my favorites and their meanings:

Let the cat out of the bag: To give away a secret.

Saved by the bell: To be rescued from a dangerous or embarrassing situation at the last possible moment.

That’s the way the ball bounces: You can’t control everything that happens and sometimes have to accept when bad or unexpected things occur.

Fly by the seat of your pants: To do something by instinct when you have no experience with the situation.

Throw in the towel: To give up or admit defeat.

Put the cart before the horse: To do things backward or in the reverse order.

A frog in your throat: Hoarseness caused by mucus in your throat.

Cool as a cucumber: To be calm in a tense or dangerous situation.

Full steam ahead: To proceed with speed and determination.

Chip off the old block: Someone who looks or behaves like his father.

Bring home the bacon: To earn money, especially for your family.

Keep your pants on: To be patient and not rush someone.

Eyes in the back of your head: The ability to sense what is going on even when your back is turned. (Parents are experts at this!)

Turn the tables: To reverse a situation and gain the upper hand, especially in a game or sporting event.

Eat like a bird: To have a small appetite.

Sweat like a pig: To sweat a lot.

The last two idioms are not accurate.

Although it may appear that birds don’t eat much compared to larger animals, they actually eat much more relative to their size. Pigs have few sweat glands so they cool off by plopping down in cool water or mud.

Bonus fact: Idioms are usually culture-specific, so one of the hardest parts of learning a foreign language is understanding its idioms. The Arabic idiom “I don’t have a camel in the caravan” means this situation doesn’t concern me.