hard shoulder vs pull-off

hard shoulder

noun
  • A verge to the side of a highway, which should be used only in case of an emergency (especially on a motorway) 

pull-off

noun
  • An area by the side of a road where vehicles may stop; a lay-by. 

  • The technique, when playing a string instrument, of using a finger of the fret hand to pluck a string by pulling the finger off the fretboard. 

adj
  • Able to be removed by pulling. 

How often have the words hard shoulder and pull-off occurred in a corpus of books? (source: Google Ngram Viewer )