etymon vs forerunner

etymon

noun
  • The original or earlier form of an inherited or borrowed word, affix, or morpheme either from an earlier period in a language's development, from an ancestral language, or from a foreign language. 

  • Meaning as derived and conveyed thereby: The literal meaning of a term according to its origin, which may differ from its usual meaning when the latter relies on idiomatic conventions that are not conveyed by the term alone (that is, they must be known in other ways, such as experience, training, education, or dictionary lookup). 

forerunner

noun
  • A forebear, an ancestor, a predecessor. 

  • By extension, a non-competitor who leads out the competitors on to the circuit, or who runs/rides the course prior to competitor trials, usually testing or checking the way. 

  • A postage stamp used in the time before a region or area issues stamps of its own. 

  • A runner at the front or ahead. 

  • A precursor or harbinger, a warning ahead. 

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