The word whim-wham (also spelled whimwham) is an Old English word (circa 1640s to 1690s) and defined as a fanciful object or a trivial and frivolous thing.  It can also mean caprice, fancy, or a sudden turn or inclination of the mind, as well as nervousness or jitters.  

Is that anything like a MacGuffin? I'm told that any sort of serious MacGuffin must be fancy, shiny, and inscrutable.