binder clip vs paper clip

binder clip

noun
  • A simple device for binding a few to many sheets of paper, leaving the sheets intact; a strip of spring steel bent into the shape of an isosceles triangle with loops at the apex. 

paper clip

noun
  • A small, folded, wire or plastic device used to hold sheets of paper together. 

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