For those who have yet to be acquanted with it, Google Ngram is a very nifty little feature that allows a user to find the frequency of certain words and phrases in a selection of 5 million books, with publication dates spanning several centuries, in an online database.
It can also yield some very interesting information about cultural trends. For instance, try the words "colour" and "color" in the British English corpus, then try again for American English:
A well-quoted example is "Marc Chagall", the name of a Jewish artist. In the German corpus, from 1933 to 1945 there is a very telling dip in the artist's popularity, due to censorship on account of World War II:
Here's another - "Iraq" in the American English corpus: