piquing vs propellant

piquing

propellant

noun
  • the explosive (cordite, gunpowder, etc) found in ammunition cartridges 

  • fuel, oxidizer, reaction mass or mixture for one or more engines (especially internal combustion engines or jet engines) that is carried within a vehicle prior to use 

  • the compressed gas in a pressurised container (especially an aerosol can) that is used to expel its content 

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