A Google Labs project, the strangely named NGram Viewer allows you to search for various words and see how their usage in books within the Google Books archive has changed over the past 200 year (or any time frame you specify).
- Computer (note the weird blip around 1900?)
- Canada (highest rate around 1830 – historians out there, any idea why?)
- Saskatchewan (nothing until the late 1960’s? Maybe reflecting the US-bias in Google’s collection?)
- Atheism (perhaps the strangest, most surprising graph of all the words I searched for!)