civil union vs shotgun wedding

civil union

noun
  • A legal union similar to marriage, established to allow same-sex couples (and, in some jurisdictions, opposite-sex couples) rights similar to those married couples have. 

shotgun wedding

noun
  • A wedding in which the bride is already pregnant. 

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

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