poor as a church mouse

To be poor as a church mouse means to be extremely poor as in regards to your finances, lack of things you own or even lack of property. This is an older idiom which shows the severity at someones bank account or lack of funds, whether due to losing their money for some reason, not having a job or simply being born in a state of poverty. Church mice have been associated with poverty for many years which is where this idiom comes from.