Google Ngram Viewer Now In "Define"

I've always found Google's definitions to be useful but yesterday I noticed they had added something useful from Google Books to their definitions: understanding a word's usage over time.

For example, a search for "define Twitter" yields:

If you expand the definition by clicking on the big downward arrow, you see a bunch of additional information including this chart of the uses of "Twitter" over time:

Google is drawing on mentions of these words in the corpus of books it has scanned as part of the Google Books project, which I had the privilege of working on while at Google. Indeed this is really just a more visible way of exposing the phenomenal Ngram viewer that Google has improved over the last few years. The Ngram viewer can be used to compare word frequencies and do lots of other interesting stuff. The database of word frequencies over time is also available to the public under the Creative Commons Attribution 3.0 Unported License so that others can build on the data. Here is a view of Twitter versus Tweet in the Ngram Viewer:

Anyhow, this may not be new to the world but it was new to me and is way cool. As the Google Books legal cases continue, it is also another great example of the value of the initiative to the public. 

PS Two more I couldn't resist adding. Good luck not spending the next half hour doing your own.

Update: And yes, there are many flaws with relying on the Ngram data to prove a point without further analysis. For examples, see Robusto's discussion on StackExchange.