Ingrid said the word chiasmus was new to her, and after visiting my site, recalled her father's riddle, which she hadn't thought about in many years. As with Mr. Young's riddle, many examples of chiasmus by letter reversal border on the profane and risque, which of course makes them even more appealing to developing minds. Some letter-reversal riddles, as you would expect, don't border on the profane and risque, they fall squarely into the category. If you're a periodic visitor to this site, you're probably familiar with implied chiasmus . If you're not, you may want to briefly explore that section before reading on.
Implied chiasmus can also occur by letter reversal.
I received a wonderful example recently from Charlie Robbins, another new friend of chiasmus. For Whom the Bell Tolls . As with all examples of implied chiasmus, half the fun comes from figuring out what's being reversed, and the rest from admiring the creativity involved in crafting the observation in the first place. I actually heard a version of this last one a few years ago while undergoing the joys of a flexible sigmoidoscopy. After explaining that it was, I asked if the expression was original with him, and he said it was not, adding that it was a common expression among urologists and oncologists.