invigilator vs tester

invigilator

noun
  • A person who supervises students during an examination; a proctor 

tester

noun
  • A person who administers a test. 

  • A miniature pot of paint for testing and comparison purposes. 

  • A cyclist who focuses on success in time trials. 

  • A device used for testing. 

  • A canopy over a bed. 

  • A sample of perfume available in a shop for customers to try before they buy. 

  • An old French silver coin. 

  • Something that overhangs something else; especially a canopy or soundboard over a pulpit. 

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