A simple letter-shift is the change of one word into another word by shifting each of its letters n steps along the alphabet. Thus, shifted three steps, the letters COLD appropriately make FROG. Similarly, but with the alphabet arranged in a circle (A following Z), it takes just nine steps to persuade the exhausted rabbit to SLEEP, BUNNY.
"Shiftgrams: My Deft Ruse,"
Word Ways: Vol. 29
, Article 16.
Available at: http://digitalcommons.butler.edu/wordways/vol29/iss1/16