If you're trying to get money from someone who won't give it, then it's like squeezing water from a stone. If you're trying to get anything from someone who refuses to give it, it's the same. It could be a feeling, confession, interest, etc

This may be a sanitised version of "You cant get blood from a stone". I don't know the origin of the saying and a (brief) Google search did not reveal the origins either. I could say, finding the origin of this saying is like squeezing blood from a stone.

No; I don't work for the tax office.

I never try that before.

I'm not that thirsty~