cotter vs cotter pin

cotter

noun
  • A pin or wedge inserted through a slot to hold machine parts together. 

  • A peasant who performed labour in exchange for the right to live in a cottage. 

  • A cotter pin. 

verb
  • To fasten with a cotter. 

cotter pin

noun
  • A pin or wedge inserted through a slot to hold machine parts together; a cotter. 

  • A split pin, the ends of which project through an object being fastened and are bent back to hold it in place. 

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