Etymology is the history of words, their origins, and how their form and meaninghave changed over time. By an extension, the term "the etymology of [a word]" means the origin of the particular word.
For languages with a long written history, etymologists make use of texts in these languages and texts about the languages to gather knowledge about how words were used during earlier periods of their history and when they entered the languages in question. Etymologists also apply the methods of comparative linguistics to reconstruct information about languages that are too old for any direct information to be available.
The word etymology is derived from the Greek word ἐτυμολογία, etymologia, itself from ἔτυμον, etymon, meaning "true sense" and the suffix -logia, denoting "the study of".