leg up vs upper hand

leg up

noun
  • A boost, a sudden improvement; an advantage, an edge. 

  • Assistance, help given to get started or overcome a problem or obstacle. 

  • The act of assisting another's progress over a wall or other obstacle by forming a step for one of their feet with one's hands. 

upper hand

noun
  • Advantage or control. 

How often have the words leg up and upper hand occurred in a corpus of books? (source: Google Ngram Viewer )