15th century "piggy bank"- Ashmolean Museum, Oxford
The origin of piggy banks dates back nearly 600 years, in a time before real banks even existed, when people commonly stored their money at home .
Dishes and cookware in Europe were made of a dense orange clay called "pygg". When people saved coins in jars made of this clay, the jars became known as "pygg banks".
Vowels in early English had different sounds than they do today. As the English language evolved, the clay (pygg) and the animal came to be pronounced the same. So, in the 19th century when English potters received requests for pygg banks they started producing banks shaped like pigs.
Intact ones are rare since you had to smash them to get your money.
This explains where the “pig” part came from, but how about the word "bank"?