driveshaft vs horizontal bar

driveshaft

noun
  • A shaft used to transmit rotary motion. 

horizontal bar

noun
  • A horizontally-aligned bar used in gymnastics, upon which acts of swinging are performed. 

  • The horizontal form of the fraction bar. 

  • A gymnastics event using the horizontal bar. 

  • The dash symbol (―) (used to introduce quoted text) 

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