lower chamber vs upper chamber

lower chamber

noun
  • The lower legislative chamber in a bicameral legislature; in many cases, the one that is directly elected and/or has more practical power, such as the power to raise and spend money. 

upper chamber

noun
  • The upper legislative chamber in a bicameral legislature; usually smaller and having more restricted power than the lower chamber. 

How often have the words lower chamber and upper chamber occurred in a corpus of books? (source: Google Ngram Viewer )