Grab the gun and bring the cat in! ?

Today I watched the DVD of the new Galactica's pilot and stumbled upon a reference. When Starbuck and Adama first meet on screen, it is implied that they know each other very well. Adama then asks her:

"What do you hear?" - "Nothing but the rain." - "Then Grab the gun and bring the cat in."

What is this? Its repeated several times in the series, sometimes partially. What a reference does it have? Maybe its line from a western, or from the original series? Its seems to be something that is meant to be familiar, it just is not for me. And what does it actually mean? Any info on that?

Ron Moore stated on his blog (http://blog.scifi.com/battlestar/) that those lines were part of a "jodie" -- a chant shouted out by troops while marching/jogging.

A cadance eh?

Never heard that one, how does the rest of it go?