Etymonline.com is a free online etymology dictionary and word origin resource that explains the history and evolution of over 30,000 English words. It was created by linguist Douglas Harper in 2001 and provides concise and informative definitions for users searching for the meaning and etymology of words. The website's database is constantly updated and includes entries for loanwords from other languages and slang expressions. It also provides links to related terms and words with similar origins. The website's user-friendly interface and thorough explanations make it a great resource for anyone interested in the history of the English language.