Poor as a church mouse

To be as poor as a church mouse is to be impecunious and dates from the 1600s although ‘hungry as a church mouse’ is also recorded from about the same time. Mice that live in churches would find very few pickings of food, if any at all, compared with mice that live in houses. Thus ‘hungry as a church mouse’ would appear to be more apt, but it is the ‘poor as’ version that has stuck.