When the word expedition was first attested in English in 1430, it referred specifically to military campaigns. Soon thereafter, it came to be used for the act of expediting, the action of sending out official documents, the state of being ready, and much more. Through Old French, the word comes from the Latin word expeditionem, which also meant "military campaign". That's from the past participle of expedire, a verb for "to prepare", and expedire is composed of the prefix ex-, meaning "out", and the root pedis, meaning "chain for the feet". So expedire, which is also the source of word verb expedite, literally meant "to free the feet from fetters", with the notion being a "liberation from difficulties". Usage of the word expedition peaked in 1626 and has been declining since.
Hello! I'm Adam Aleksic, a rising junior studying government and linguistics at Harvard University, where I co-founded the Harvard Undergraduate Linguistics Society. In addition to etymology, I also really enjoy trivia, politics, vexillology, geography, board games, conlanging, art history, and law.