Some connotation from Elizabethan witch days still clings in these Anglo-saxon parts to a frog or toad. " Eye of newt and toe of frog" in the litany of Macbeth's witches has its counterpart here.
Now, when I hear triple witching day, I imagine a boiling cauldron on the floor of the stock exchange, and around it are three shadowy figures... ... Eye of newt and toe of frog... ... Wool of bat and tongue of dog.