Idioms Can Be Idiotic

I do not know if other languages have many of them, but English has so many idiotic idioms.

Idioms are quaint little sayings that we take for granted when we are native speakers. We just know that other people know what certain phrases mean. Even though they do not seem to have anything to do with the subject we are talking about.

“Packed in like sardines.” (Lots of people in this place.)
“Filled to the gills.” (Overate.)
“Dead as a doornail.” (Dead.)
“You know the drill.” (You know what ...