blackmail vs hold to ransom

blackmail

verb
  • To extort money or favors from (a person) by exciting fears of injury other than bodily harm, such as injury to reputation, distress of mind, false accusation, etc. 

  • To speak ill of someone; to defame someone. 

noun
  • The extortion of money or favours by threats of public accusation, exposure, or censure. 

  • Black rent, or rent paid in corn, meat, or the lowest coin, as opposed to white rent, which was paid in silver. 

  • Compromising material that can be used to extort someone, dirt. 

hold to ransom

verb
  • To hold (someone) hostage until a ransom is paid. 

How often have the words blackmail and hold to ransom occurred in a corpus of books? (source: Google Ngram Viewer )