"Hubble Bubble (Toil and Trouble)"

Recently, I ran across the phrase "toil and trouble," which reminded me of some lines in Shakespeare's Macbeth, where the witches say:

Double, double, toil and trouble;

Fire burn and caldron bubble.  (IV.i.10-11) 

This, in turn, reminded me of the Manfred Mann song "Hubble Bubble (Toil and Trouble)," which I have only on a vinyl re-print of the American version of The Five Faces of Manfred Mann.  I listened to the record again and paid close attention to that song, and while it seems obvious enough that the title line was inspired by Shakespeare, there's not really anything else that connects the song to the play.