front runner vs mother ship

front runner

noun
  • One who engages in front running. 

  • Any of the most likely winners in a contest, election, etc. 

mother ship

noun
  • A vessel or aircraft that serves or carries a smaller vessel or vessels that operate independently from it. 

  • Fond term of address for one's mother. 

How often have the words front runner and mother ship occurred in a corpus of books? (source: Google Ngram Viewer )