Tug the Cox,
thanks for sharing where that rhyme "Mrs. D" rhyme comes from. I confess that I'm not familiar with Roald Dahl's books and had to look up the information about "Matilda" online. Here's a link to the Wikipedia page for that 1988 book which was adapted to a film in 1996.

http://en.wikipedia.org/wiki/Matilda_(novel)