impede vs stonewall

impede

verb
  • To get in the way of; to hinder. 

stonewall

verb
  • To obstruct. 

  • To refuse to answer or cooperate, especially in supplying information. 

noun
  • An obstruction. 

  • An alcoholic drink popular in colonial America, consisting of apple cider (or sometimes applejack) mixed with rum (or sometimes gin or whisky). 

  • A refusal to cooperate. 

adj
  • Certain, definite. 

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