old man vs senior captain

old man

noun
  • A unit's commanding officer, or the commander of a naval vessel, irrespective of age. 

  • The state of human nature without the spiritual transformation brought about by redemption through Jesus Christ. 

  • Synonym of southernwood 

  • An elderly man. 

  • A husband, or male significant other, irrespective of age. 

  • Used attributively to denote something of exceptional size, strength, age etc. 

  • One's father. 

  • One's male employer, irrespective of age. 

senior captain

noun
  • a military rank for a naval officer above that of captain and below the admiral ranks or flag ranks 

  • a military rank for a field officer above that of captain and below that of major 

How often have the words old man and senior captain occurred in a corpus of books? (source: Google Ngram Viewer )