Writer's constipation

If I had nothing to do all day but sit and write, I wonder how many pages I could turn out. I'm certain it would all be crap, or mostly crap, but producing crap is better than producing nothing at all.

Seems like I've had a lot of writer's block lately. Why is it called "writer's block"? Seems more like "writer's constipation": I know there's something in there. I really want to push it out. My body aches with the strain of effort, yet nothing comes. At most, a dingleberry or two.