footfall vs stepping

footfall

noun
  • The sound made by a footstep; also, the footstep or step itself. 

  • The number of pedestrians going into or passing through a place (especially a commercial venue such as a shop) during a specified time period; also, the pedestrians in a particular place regarded collectively; foot traffic. 

stepping

noun
  • The act of taking a step. 

  • A specific iteration of a model of central processing unit, often distinguished by the addition or removal of features compared to earlier examples of the same processor, or the presence, or lack thereof, of specific bugs. 

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