You give me pause

A friend of mine said to me recently, "You give me pause." I'm not entirely sure what she meant by this, and I was wondering if you could help with the meaning and origin of the phrase.

I can't help with the origin, Brian, but I've always understood something that 'gives you pause' causes you to reconsider the matter at hand; perhaps to look at things from a different perspective. You won't necessarily change your mind but you'll defer any conclusions you might have reached or any action you might have taken.

I agree. I think it's a shortening of 'pause for thought' as in 'hmmm... that's given me pause for thought' (that's given me something to think about).