Oxford English Dictionary (OED) Online

If you’ve never poked around the OED (Oxford English Dictionary) online, what are you waiting for? It’s not just for etymologists; it’s for anyone interested in language change or even just understanding what’s going on with English currently. If you’re not familiar with the OED, the key thing to know about it is its creators strive to record the earliest instance of use of any given word, so it’s packed with quotations of how words have been used over time. Or, as its website puts it, “The Oxford English Dictionary (OED) is […] is an unsurpassed guide to the meaning, history, and pronunciation of 600,000 words— past and present—from across the English-speaking world.

Bonus: There’s a cool book about the 70-year process of creating it called The Professor & The Madman: A Tale of Murder, Insanity, and the Making of the Oxford English Dictionary.

*Note: You may need to sign on to your university’s VPN (virtual private network) or equivalent in order to fully use the OED online, or have unlimited use of it, but it appears to offer a lot for free.