vigil vs watch person watchtower

vigil

noun
  • A quiet demonstration in support of a cause. 

  • A period of observation or surveillance at any hour. 

  • An instance of keeping awake during normal sleeping hours, especially to keep watch or pray. 

  • The eve of a religious festival in which staying awake is part of the ritual devotions. 

watch person watchtower

How often have the words vigil and watch person watchtower occurred in a corpus of books? (source: Google Ngram Viewer )