I've been wrong umpteen times before, and this is probably no exception. Could this have nothing to do with money? I think it may be to do with bricklaying ( cf English and Flemish bonds ). Diaper is a diamond shaped pattern in walls.
Thanks Josh....yes, it is to do with bricklaying. It was a question in a quiz a while back. I took a chance thinking that it was to do with stocks/shares whatever, but you're right.