I was just wondering:

What does the “knee-jerk” part of the phrase “knee-jerk liberal refer to?  Or, in other words, what is a liberal like myself supposedly jerking her knees about?

It makes me imagine a form of folk dance with lots of bouncing involved.  And little bands of bells around the ankles to jingle while those knees are doing their thing.

But this is a derogatory term.  So what’s the story?