Ward Cunningham writes on WardsWiki (referring to Kent Beck):
I would often ask Kent, “What is the
simplest thing we can program that
will convince us we are on the right
track?” Such stepping outside the
difficulties at hand often led us to
simpler and more compelling solutions.
Kent dubbed this a Spike. I found the
practice particularly useful while
maintaining large frameworks.
Kent Beck writes in Guide to Better Smalltalk:
Sometimes I call this a “spike,” because we are driving a spike through the entire design. […] Because people variously associate “spike” with volleyball, railroads, or dogs, I have begun using “architectural prototype” to describe this implementation.