From:
http://www.quinion.com/words/qa/qa-jur1.htm

 From Robert Williams: "I'd seen the phrase jerry
 rigged and assumed it was related to WWII and the
 efforts of German soldiers to keep things running by
 patching things together. However I've also seen it
 spelled jury rigged. Where does this expression come
 from?"

 It's much older than World War Two. In the form jury
 rigged it's from the days of sailing ships and dates
 from the early 1600s, if not earlier. It refers to a
 mast which is makeshift or a temporary contrivance,
 perhaps because the original was lost or damaged in a
 storm. Nobody knows for sure where it comes from. It
 has been suggested that it's a shortening of
 "injury-rigged", though that sounds to me like
 something invented well after the event. Another
 suggestion often made is that it comes from the old
 French ajurie, "aid, assistance".

 I swear I'll stop now.......................