bit part vs redshirt

bit part

noun
  • A minor role, generally not assigned a name. 

redshirt

noun
  • An unimportant character introduced only to be killed in order to underscore the peril to the important characters; an expendable character. 

  • An athlete who spends a year not participating in official athletic activities, but does not lose his or her eligibility to participate in following years. 

  • A person responsible for loading and unloading weapons, artillery, and equipment from aircraft. 

verb
  • To take on a status wherein one will spend a year not participating in official athletic activities. 

  • To hold a child out of kindergarten for one year in the hope that the child will do better academically and socially. 

  • To place an athlete in a status wherein the athlete will spend a year not participating in official athletic activities, but will not lose his or her eligibility to participate in following years. 

  • The university decided to redshirt the freshman linebacker to give him an extra year to build up his bulk. 

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