Oh, Thank you Thomas for this interesting piece of information.
Wikipedia confused me, I guess...
"Piggy bank (sometimes penny bank or money box) is the traditional name of a coin accumulation and storage receptacle; it is most often, but not exclusively, used by children. "
Wikipedia
Oh, Wikipedia does mention something similar to that..
"In Middle English, "pygg" referred to a type of clay used for making various household objects such as jars.
People often saved money in kitchen pots and jars made of pygg, called "pygg jars". By the 18th century, the spelling of "pygg" had changed and the term
"pygg jar" had evolved to "pig bank." [3] 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."
Wikipedia
