a church mouse 表达“穷到吃土，一贫如洗”中世纪的西方教堂里（church）是没有放食物的柜子和储物室的，所以住在那里的老鼠总是挨饿。后来，老鼠就成了“贫穷”的象征。

【例句】
With his company doing bankrupt, he is now as poor as a church mouse.
随着他的公司倒闭破产，他目前已是一贫如洗。

When I last saw him, he was as poor as a church mouse.
我上次见到他的时候，他已经一贫如洗了。