advisor vs informer

advisor

noun
  • One who offers advice. 

  • A xiangqi piece, that is moved one point diagonally and confined within the palace. 

informer

noun
  • One who informs someone else about something. 

  • One who informs, animates, or inspires. 

  • A person who tells authorities about improper or illegal activity. 

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