promotion vs stumbling block

promotion

noun
  • An event intended to increase the reach or image of a product or brand. 

  • Transformation of a pawn into a piece (by reaching the opponent's back rank). 

  • Dissemination of information in order to increase its popularity. 

  • Forward motion. (Contrast remotion.) 

  • An advancement in rank or position. 

stumbling block

noun
  • A hindrance, obstacle or impediment; an opportunity for error. 

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