Charting conceptual history

Google’s Ngram is a nifty tool for researching historical word use, such as the first use of a word/phrase, or how its popularity changes over time. Ngram is 10 years old, but it got a significant upgrade last year so now it includes a lot more old books. I use Ngram to visualize — to a first approximation — the relative importance of a concept over time. Its cool interface lets me click on a date range, and then it will show me excerpts from the historical books from that date with that word or phrase. — KK