A word possesses a shiftgram if its letters can first be shifted along the alphabet and then transposed to form another word. The classic example MUSIC to QUACK was offered by Alice Gorki and Dimitri Miller in "Sea-Changed Words" in the February 1969 Word Ways.
Eckler, A. Ross
"How Many Shiftgrams in a Word-Set?,"
Word Ways: Vol. 43
, Article 23.
Available at: http://digitalcommons.butler.edu/wordways/vol43/iss1/23