Simplify the following text for a Grade 2 native English-speaking person.
Original: 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 . ''
Simplified: But some say that `` Piggy '' was `` Pygg '' at first .