This is part of the witch's spell in Macbeth (William Shakespear):
In the caldron boil and bake;
Eye of newt, and toe of frog,
Wool of bat, and tongue of dog,
Adder's fork, and blind-worm's sting,
Lizard's leg, and owlet's wing,--
For a charm of powerful trouble,
Like a hell-broth boil and bubble.
Of course these words could be taken literally, but is it possible that this and other spells were written (or spoken) in a sort of code, as below:
'Eye of Newt' represents 'mustard seeds'
Toe of Frog is also known as 'bulbous buttercups'
In 1518 Sir Marmaduke Constable, who had fought in several major battles served under six kings, died. His death was caused be swallowing a frog when he drank water. Perhaps it wasn't an actual frog which he swallowed but a potion containing bulbous buttercups!