impediment vs restrainer

impediment

noun
  • A hindrance; that which impedes or obstructs progress. 

  • Baggage, especially that of an army; impedimenta. 

  • A disability, especially one affecting the hearing or speech. 

restrainer

noun
  • Something that restrains 

  • A chemical compound (such as potassium bromide), added to a developer to prevent fogging 

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