The dataset comes from google books in various languages.<p>Be sure to visualize your own queries at:
<a href="http://ngrams.googlelabs.com/" rel="nofollow">http://ngrams.googlelabs.com/</a><p>I've got the info from this article:
<a href="http://www.technologyreview.com/computing/26937/" rel="nofollow">http://www.technologyreview.com/computing/26937/</a>