beholder vs signaller

beholder

noun
  • Someone who observes or beholds; an observer or spectator. 

  • A fictional monster in roleplaying games, a floating orb of flesh with a large mouth and many eyes on stalks. 

signaller

noun
  • One who signals. 

  • synonym of signalman 

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