lower house vs sole house

lower house

noun
  • The lower legislative house 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. 

  • Coordinate terms: upper house, sole house 

sole house

noun
  • The single legislative house of a unicameral legislature. 

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