A、It held dirt well. B、It was long-lasting. C、It symbolized wealth. D、It was inexpensive. D因果判断题。中世纪时，由于矿物质稀少而昂贵，他们极少用于家用器皿的大批量生

Where did the term Piggy Bank come from? Today the simple piggy bank is seen everywhere as the symbol of saving and frugality, for putting away funds for a rainy day, or building a nest egg for life’s sudden money needs, such as paying  college expenses, buying a home, or financing retirement. But why a pig? Dogs bury bones for a rainy day. Why not a dog shaped bank for coins? Squirrels are well known hoarders too and we talk about squirreling away valuables, why not a bank in the shape of a squirrel? Well nevertheless, for 300 years, children’s banks have been imitation pigs with slots in the back. Charles Bernardy, the author of Extraordinary Origins of Everyday Things, tells how the symbol came about by coincidence. According to Bernardy, during the middle ages, mined metal was scarce and expensive, therefore was rarely used in the manufacture of household utensils. The type of orange clay, known of pygg, spelt p-y-g-g, was more abundant and economical throughout western Europe. It was used in making dishes, cups, pots and jars. And so these earthenware items were referred to as pygg. Frugal people saved cash in kitchen pots and jars. Although a pygg jar was not originally shaped like a pig, the name persisted. However, by the 18th century, pygg, p-y-g-g jar became pig, p-i- g jar or pig bank. Potters had simply begun to east the bank in the shape of its common name. In the United States, the popular piggy bank has always been a symbol of saving money.