big wheel vs observation wheel

big wheel

noun
  • A Ferris wheel. 

  • A person with a great deal of power or influence, especially a high-ranking person in an organization. 

  • A low-riding tricycle with a large front wheel. 

observation wheel

noun
  • Ferris wheel 

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