life savings vs piggy bank

life savings

noun
  • A large sum of money one has saved over a considerable number of years. 

piggy bank

noun
  • A small container, sometimes in the form of a pig, to store small saved coins in. Often the "bank" must be broken open to retrieve the contents. 

How often have the words life savings and piggy bank occurred in a corpus of books? (source: Google Ngram Viewer )