decapitation vs impalement

decapitation

noun
  • Beheading; the act of beheading or decapitating. 

  • The ousting or destruction of the ruling body of a government or other organization. 

  • The unseating of a senior politician. 

impalement

noun
  • The act of torturing or executing someone by impaling them on a sharp stake. 

  • (obsolete) In the sense of an enclosure, the calyx of a flower. In still older works, also spelt empalement (q.v.) 

  • A space fenced in, such as by palings, possibly in the form of an enclosure or cup. 

  • The joining of two coats of arms on one shield. 

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