Reaching a bit, but this answer on Judaism.SE tentatively suggests that aliens are alluded to indirectly in the Bible (Judges 5.23 in the English/Christian version). The book in question would have been written before 500 BCE, and the interpretation of the verse as referring to off-worlders presumably dates back to at least 200 CE (the linked answer attributes it to Mo'ed Kattan which AIUI is part of the Mishnah).
If nothing else, this (in combination with Lucian) probably indicates that the concept was no longer unique and had entered mainstream culture by that point.
N.B. since the question asks about the history of the concept, I reckon the Bible's status as a work of fiction or non-fiction is completely irrelevant to this answer.