Why is the pig a symbol of money and home banks?

Answer 1

In the middle ages the money-boxes were made of a orange clay called pygg. Because the sound of pygg over the centuries evolved to sound like pig; someone, maybe mistakenly, thought that the word referred to the shape (rather than the material) and started making the pots in the shape of the pig. The piggy-boxes became "fashionable" and are still in use today. So the shape of the pig became associated with money.