astern of vs via

astern of

prep
  • behind 

via

prep
  • By way of; passing through. 

  • By (means of); using. 

noun
  • A main road or highway, especially in ancient Rome. (Mainly used in set phrases, below.) 

  • A small hole in a printed circuit board filled with metal which connects two or more layers. 

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