Blue lyrics, Cecil article

So, in todays archive column, The Perfect Master, in addressing the question of John the Conqueroo root, makes a reference to a ‘Jack’ as a different kind of spell/charm/voodo thingy.

Now I acknowledge that Jack is pretty generic word with lots of usage, but I’m interested in some blues lyrics that mention a Jack in the context of a charm as Cecil used it.

http://www.straightdope.com/columns/read/284/what-is-the-john-the-conqueroo-made-famous-by-blues-singers