clapper vs observer

clapper

noun
  • A slapshot 

  • A clapstick (musical instrument). 

  • A pounding block. 

  • A wooden mechanical device used as a scarecrow; bird-scaring rattle, a wind-rattle or a wind-clapper. 

  • The chattering damsel of a mill. 

  • An object so suspended inside a bell that it may hit the bell and cause it to ring; a clanger or tongue. 

  • The hinged part of a clapperboard, used to synchronise images and soundtrack, or the clapperboard itself. 

  • One who claps; a person who applauds by clapping the hands. 

verb
  • To make a repetitive clapping sound; to clatter. 

  • Of birds, to repeatedly strike the mandibles together. 

  • To ring a bell by pulling a rope attached to the clapper. 

observer

noun
  • A sentry etc. manning an observation post 

  • One who makes observations, monitors or takes notice 

  • A crew member on an aircraft who makes observations of enemy positions or aircraft 

  • A person sent as a representative, to a meeting or other function to monitor but not to participate 

  • One who adheres or follows laws, guidelines, etc. 

  • A country or other entity which has limited participation rights within an organization. 

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