impediment vs obstruction

impediment

noun
  • A hindrance; that which impedes or obstructs progress. 

  • Baggage, especially that of an army; impedimenta. 

  • A disability, especially one affecting the hearing or speech. 

obstruction

noun
  • Something which obstructs or impedes, either intentionally or unintentionally 

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

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

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