damper vs restriction

damper

noun
  • A contrivance (sordine), as in a pianoforte, to deaden vibrations; or, as in other pieces of mechanism, to check some action at a particular time. 

  • A device that decreases the oscillations of a system. 

  • A shock absorber. 

  • A valve or movable plate in the flue or other part of a stove, furnace, etc., used to check or regulate the draught of air. 

  • Bread made from a basic recipe of flour, water, milk, and salt, but without yeast. 

  • Something that kills the mood. 

restriction

noun
  • A regulation or limitation that restricts. 

  • The act of restricting, or the state of being restricted. 

  • The mechanism by which a cell degrades foreign DNA material. 

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