building society vs commercial bank

building society

noun
  • A type of financial institution which traditionally was based on lending money (as mortgages) to society members to buy houses, from other members pooled savings and/or money borrowed wholesale. 

commercial bank

noun
  • A bank whose chief business is accepting demand deposits and making short-term loans. 

How often have the words building society and commercial bank occurred in a corpus of books? (source: Google Ngram Viewer )