retelling vs trial balloon

retelling

noun
  • A new, changed, or adapted version of a story. 

trial balloon

noun
  • A small balloon released into the sky to determine the direction and tendency of winds in the upper air before a manned ascent in a larger balloon; a ballon d'essai. 

  • An idea, suggestion, or prospective action, product, etc., offered to an audience or group in order to test whether it generates acceptance or interest. 

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