obstruction vs stonewalling

obstruction

noun
  • The act of obstructing, or state of being obstructed. 

  • Something which obstructs or impedes, either intentionally or unintentionally 

  • The condition of having the natural powers obstructed in their usual course; the arrest of the vital functions; death. 

stonewalling

noun
  • A refusal to answer or to cooperate. 

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