ad vs waymark

ad

prep
  • to, toward 

noun
  • advantage 

waymark

noun
  • A sign or symbol marked in a prominent position in an off-road location to show the track of a footpath or route; fingerpost; guidepost; milestone. 

  • A map coordinate stored within a satellite navigation system 

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