gassing vs lethal injection

gassing

noun
  • Poisoning by noxious gas. 

  • boasting; insincere or empty talk 

  • Any similar process of singeing. 

  • The process of passing cotton goods between two rollers and exposing them to numerous minute jets of gas to burn off the small fibres. 

  • The liberation of hydrogen from an overcharged battery due to electrolysis of the electrolyte. 

lethal injection

noun
  • A means of execution or of euthanasia in which a person is injected with a fatal dose of drugs. 

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