Dr vs gentleman

Dr

noun
  • debitor 

  • debit 

  • Doctor, a title used before a doctor's name or surname (Dr Jane Doe, Dr Doe) 

  • drive, used in street names 

gentleman

noun
  • An amateur player, particularly one whose wealth permits him to forego payment. 

  • Any well-bred, well-mannered, or charming man. 

  • Any man. 

  • An amateur or dabbler in any field, particularly those of independent means. 

  • An effeminate or oversophisticated man. 

  • A man of gentle but not noble birth, particularly a man of means (originally ownership of property) who does not work for a living but has no official status in a peerage; (UK law) an armiferous man ranking below a knight. 

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