Wordorigins.org

Google Books search engine.

Google’s project for digitization of printed books. An excellent and growing database of works. The search engine, however, is not particularly well suited for searching exact text matches—the algorithms are designed to find topics, not specific phrases. And the dates given by the search engine are not to be relied upon—they are highly inaccurate, sometimes off by centuries. Check the title page of any work found by the search engine to verify the date is correct.