professor vs schoolmaster

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. 

schoolmaster

noun
  • Male teacher in charge of a school, usually a small one. 

  • Anything that teaches. 

  • A male teacher. 

verb
  • To teach in the capacity of schoolmaster. 

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