Oxford English Dictionary

The Oxford English Dictionary (OED) is the principal historical dictionary of the English language, published by Oxford University Press (OUP), a University of Oxford publishing house. The dictionary, which began publication in 1884, traces the historical development of the English language, providing a comprehensive resource to scholars and academic researchers, and provides ongoing descriptions of English language usage in its variations around the world.

Source: Wikipedia — Oxford English Dictionary (CC BY-SA 4.0)