The Oxford English Dictionary
The Oxford English Dictionary is our largest English dictionary. Some of its more useful features are etymologies, and chronologies of usage.
Use the English Dictionary to learn about the history of words, where they first appeared, and how they have changed. You can find around when people first began abbreviating their consternation as WTF (1985), what language the word opossum comes from (Algonquin), or what words meant to English speakers of different eras.