isochronous vs level pegging

isochronous

adj
  • Happening at the same time; simultaneous. 

  • Happening at regular intervals; isochronal. 

  • of or pertaining to data associated with time-sensitive applications. 

  • Of or pertaining to the use of clocks derived from the same clock reference. 

level pegging

adj
  • equal (having the same number of points, or being in the same position) 

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