flotation vs underpinning

flotation

noun
  • A state of floating, or being afloat. 

  • The ability (as of a tire or snowshoes) to stay on the surface of soft ground or snow. 

  • A process of separating minerals by agitating a mixture with water and detergents etc; selected substances being carried to the surface in air bubbles. 

  • The launching onto the market of a tranche of stocks or shares, usually a new issue. 

underpinning

noun
  • The lower body or legs. 

  • A support or foundation, especially as a structure of masonry that supports a wall. 

  • A basis for something. 

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