gassing vs rub out

gassing

noun
  • 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. 

  • Poisoning by noxious gas. 

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

rub out

verb
  • To delete or erase or remove (something) by rubbing. 

  • To kill, especially to murder. 

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