the.com/alien

means Strange, foreign, or not of this world — a being, idea, or thing that comes from (or feels like it comes from) somewhere fundamentally outside what's familiar.

from From Latin alienus, 'belonging to another,' built on alius, 'other.' For most of its life in English it simply meant 'foreign' — an alien was any outsider from another country, no spaceship required. The jump to 'extraterrestrial' is a modern, 20th-century narrowing, as science fiction borrowed the word for visitors whose 'other country' turned out to be another planet entirely.