“er bai wu”( the dialect in south of China, people may say "er bei wu" ) is a figure "250“,means:"fool, stupid or mad". In ancient Chian, the 500 liang(a unit of weight equal to 50 grams in China) of silver we called one feng(a unit of money in ancient China),"feng" is similar to ”疯"(mad,fool) in pronunciation, so the 250 ,the half of 500, means “半疯半傻"(half of mad,fool).