fella vs sir

fella

noun
  • Used as a term of address for a male person. 

  • Used as a general intensifier; a pfella. 

sir

noun
  • A respectful term of address to an adult male (often older), especially if his name or proper title is unknown. 

  • A man of a higher rank or position. 

  • to a teacher. 

  • to a knight or other low member of the peerage. 

  • to a superior military officer. 

  • A respectful term of address to a man of higher rank or position 

verb
  • To address (someone) using "sir". 

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