title: How to search Google Ngrams for "dated" words & phrases?
body: <p>I'd like to write an application that searches Google's Ngram data to return words and phrases that used to be more popular, by some arbitrary percentage, within some arbitrary range of years, than they are now.</p>
  
  <p>For example: <a href="https://books.google.com/ngrams/graph?content=cowabunga&amp;year_start=1950&amp;year_end=2000&amp;corpus=15&amp;smoothing=3" rel="nofollow">https://books.google.com/ngrams/graph?content=cowabunga&amp;year_start=1950&amp;year_end=2000&amp;corpus=15&amp;smoothing=3</a></p>
  
  <p>Ideally, I'd like to be able to <strong>find</strong> these words and phrases without specifying them up front. Can anyone help me come up with a way to do this using a downloaded copy of the Ngrams data?</p>