pulley vs tractor

pulley

noun
  • One of the simple machines; a sheave, a wheel with a grooved rim, in which a pulled rope or chain lifts an object (more useful when two or more pulleys are used together, as in a block and tackle arrangement, such that a small force moving through a greater distance can exert a larger force through a smaller distance). 

verb
  • To raise or lift by means of a pulley. 

tractor

noun
  • Any piece of machinery that pulls something. 

  • A vehicle used in farms e.g. for pulling farm equipment and preparing the fields. 

  • A truck (or lorry) for pulling a semi-trailer or trailer. 

  • An aeroplane where the propeller is located in front of the fuselage. 

  • A British Rail Class 37 locomotive. 

  • A movable coop without a floor to allow for free ranging. 

verb
  • To move with a tractor beam. 

  • To prepare (land) with a tractor. 

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