blowgun vs nerve gas

blowgun

noun
  • A hollow tube through which a dart or similar missile may be blown. 

nerve gas

noun
  • A toxic chemical compound and banned weapon of mass destruction which, when inhaled or ingested, impairs nervous system functions, typically causing extreme physical distress and death by asphyxiation. 

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