We are fortunate to have quick and easy access to the largest historical dictionary of English ever published: the Oxford English Dictionary. The OED is designed to provide the history of meaning and use of almost all words in the English language, from 1100 through the late twentieth century, with illustrative quotations. The OED is restricted to UCM users, so if you are accessing it off campus, you’ll need to log on via the VPN. Instructions on how to do that are available here.
Professor Adan-Lifante recommends the Diccionario de la Real Academia de la Lengua Española. You do not need to be logged in via the VPN to use this online dictionary.