guru vs professor

guru

noun
  • An influential advisor or mentor. 

  • In Indian traditions,it means a knowlegable teacher who guides his shishya(disciple/lit. seeker of [of knowledge or truth]) 

  • A Hindu or Sikh spiritual teacher. 

verb
  • To act as a guru; to give wise advice 

professor

noun
  • A teacher or faculty member at a college or university regardless of formal rank. 

  • The most senior rank for an academic at a university or similar institution, informally also known as "full professor." 

  • A pianist in a saloon, brothel, etc. 

  • The puppeteer who performs a Punch and Judy show; a Punchman. 

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