bells vs shotgun wedding

bells

noun
  • Ship's bells; the strokes on a ship's bell, every half-hour, to mark the passage of time. 

shotgun wedding

noun
  • Any similarly reputedly forced partnership, between people, organizations, components, or concepts. 

  • A wedding in which the bride is already pregnant. 

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