contour vs pair of compasses

contour

noun
  • An outline, boundary or border, usually of curved shape. 

  • a speech sound which behaves as a single segment, but which makes an internal transition from one quality, place, or manner to another. 

  • A line on a map or chart delineating those points which have the same altitude or other plotted quantity: a contour line or isopleth. 

  • A general description giving the most important points. 

verb
  • To mark with contour lines. 

  • To form a more or less curved boundary or border upon. 

  • To practise the makeup technique of contouring. 

pair of compasses

noun
  • A tool for drawing accurate circles or arches, usually consisting of two arms joined at one end in such a way that the arms can be opened and closed; one of the arms is pointed at its free end while the other holds a pencil, pencil lead or some other implement for making marks. 

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