co-father vs old man

co-father

noun
  • In a male homosexual couple, the nonbiological father (partner of the biological father) of a child. 

old man

noun
  • A husband, or male significant other, 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. 

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

  • One's father. 

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

  • One's male employer, irrespective of age. 

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