In earlier times, metal was expensive and seldom used for household wares. Instead, dishes and pots were made of an economical clay called pygg. Whenever housewives could save an extra coin, they dropped it into one of their clay jars.They called this their pygg bank or their piggy bank. When an English potter misunderstood the word, he made a bank that resembled a pig, and it caught on. This name caught on because the pig banks were mostly used by children, and a pig is a child-friendly shape that is easy to make out of clay. Once the meaning had transferred from the substance to the shape, piggy banks began to be made from other substances, including glass, plaster, and plastic.