“The pot calling the kettle black.”

In the seventeenth century, both pots and kettles turned black because they were used over open fires. Today, this idiom means criticizing someone else for a fault of one's own.

“Raining cats and dogs.”

In Norse mythology, the dog is associated with wind and the cat with storms. This expression means it's raining very heavily.

To “shed crocodile tears.”

Crocodiles have a reflex that causes their eyes to tear when they open their mouths. This makes it look as though they are crying while devouring their prey. In fact, neither crocodiles nor people who shed “crocodile” tears feel sorry for their actions.

“Clean bill of health.”

When a doctor gives you a “clean bill of health,” you know that you’re perfectly healthy. In the past, when a ship left a port, it was given a Bill of Health if there were no epidemics in the area from which it left.

“Close but no cigar.”

Years ago, cigars were often given as prizes in contests at fairs and carnivals. When a player almost won, the person running the game would say, “Close but no cigar.”