exponent vs lead character

exponent

noun
  • One who expounds, represents or advocates. 

  • The part of a floating-point number that represents its exponent value. 

  • The number by which a value (called the base) is said to be raised to a power in exponentiation: for example, the 3 in 2³=8. 

  • A manifestation of a morphosyntactic property. 

lead character

noun
  • The main protagonist in a work. 

How often have the words exponent and lead character occurred in a corpus of books? (source: Google Ngram Viewer )