crankshaft vs kingpin

crankshaft

noun
  • A rotating shaft that drives (or is driven by) a crank. 

verb
  • To deform in such a manner that part of the rod or bolt is displaced sideways, offset from the longitudinal axis of the part, but remains parallel with the part's main longitudinal axis, with the final shape somewhat resembling a crankshaft. 

kingpin

noun
  • The axis around which steered wheels pivot; a bolt that holds the axis in place—a kingbolt. 

  • The bolt holding together the truck of a roller skate or skateboard. 

  • The pivot or connector between a tractor and trailer in the fifth-wheel coupling of semi-trailer truck. 

  • The pin at the centre of the triangle of bowling pins (originally the tallest pin in kayles). Sometimes also the headpin at the apex. 

  • The most important person in an undertaking or organization. 

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