Happy World UFO day! The first use of the word alien as meaning "extraterrestrial" was in 1953 in a science fiction magazine. Before that it meant "foreigner", a definition that also still exists today. Much before, it came into English in the fourteenth century from French aliene, from the Latin word alienus, which also meant "foreigner" but earlier had a more literal meaning of "belonging to someone else". This is from alius, which meant "other" (and is the direct etymon of alias, "other name", through Latin alias). It is then theorized that this could all go back to the Proto-Indo-European root al, which meant "beyond". There is some debate about this, however; sonce we're just reconstructing this, it may also be something like el or hel. Whatever the case, that same root lead to the Proto-Germanic root aljaz ("other" as well), which lead to the Old English word elles, which had a similar definition and was the forefather of the adverb else. All these words aren't alien; they're nothing else than the aliases of one root word!
Hello! I'm Adam Aleksic, a sophomore studying government and linguistics at Harvard University, where I co-founded the Harvard Undergraduate Linguistics Society. In addition to etymology, I also really enjoy politics, vexillology, geography, board games, conlanging, and law.