speedometer vs tachymeter

speedometer

noun
  • An instrument located within the dashboard of a vehicle that measures and indicates the current speed of the vehicle. 

  • Such a device incorporating an odometer. 

tachymeter

noun
  • A speed indicator; a tachometer. 

  • A surveying instrument for quickly finding distances. 

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