Idiom: an expression, word, or phrase that has a figurative meaning that is comprehended in regard to a common use of that expression that is separate from the literal meaning or definition of the words of which it is made.
The longer I teach the more a realize how lost the art of wordplay, such as idiom recognition and use, has become. Occasionally during a lesson, I'll crack wise with one slightly tweaked idiom or another, such as "You are as sharp as a pillow," an obvious play on the more common (and inherently complimentary) "sharp as a tack." In almost every case it is greeted with a smile, only rarely following a pause so that the recipient may better understand what is being implied (translation: "that wasn't very smart!").
This morning when one student asked for permission to use the bathroom, I attempted to formulate a similar ironic play on the saying "be back in two-shakes of a lamb's tail." While the original expression is intended to suggest doing something quickly, fully aware that it is rare to have a high school student leave and return from the restroom quickly, I attempted to pull together an appropriate idiom, one intended to imply that he would likely be back only after a lo-o-o-ng trip to the potty. It was at that time that I drew a blank about what kind of animal (other than man) has no tail.
It was at this time that I stifled my initial impulse to say something and signed the hall pass. I also made a note to check on the Internet when I made it home after school to see if I could conclude my idiom. The goal would be to find a tailless "animal" that was common enough to be accessible to my teenage charges.
As is often the case, it was I who was guilty of being "sharp as a pillow."
After a quickie search I was embarrassed to find that the answer was right in front of me the whole time. In fact (depending on your feelings about evolution) it was me. Or you. Primates do not have tails: gorillas, chimpanzees, and orangutans. It is one thing that defines them and us as humans are part of the primate family. Armed with this knowledge I am now fully armed with the following should the situation (which it most surely will) arises for its use again: "Be sure to be back in two shakes of an ape's tail."