groundbreaker vs pioneer

groundbreaker

noun
  • First person to do, make or fight for something. A pioneer; a seminal person. 

pioneer

noun
  • A person or other entity who is first or among the earliest in any field of inquiry, enterprise, or progress. 

  • A member of a children’s organization operated by the Communist Party, typically in the second of three stages toward becoming an member of the Party itself. 

  • One who goes before, as into the wilderness, preparing the way for others to follow. 

  • Some people will consider their national heroes to be pioneers of civilization. 

  • A member of any of several European organizations advocating abstinence from alcohol. 

verb
  • To be the first to do or achieve (something), preparing the way for others to follow. 

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