odometer vs tachometer

odometer

noun
  • An instrument, usually embedded within the speedometer of a vehicle, that measures the distance the vehicle has traveled since production. 

  • A wheel used by surveyors, which registers distance traveled. 

tachometer

noun
  • A device for measuring or indicating velocity or speed, as of blood, a river, a machine, etc. 

  • A device for measuring the revolutions per minute (RPMs) of a revolving shaft, as with the driveshaft of an automobile. 

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