Apropos what @WizardOfDocs just posted: ξένος, as an adjective in Hellenic Greek, meant "foreign" or "strange, unusual". It's where we get the English prefix "xeno-".
But as a noun, ξένος had a remarkably different meaning: it meant "guest" or "host", in the sense of "one receiving/presenting hospitality". Prof. Heiny, my Classical Studies teacher, liked to translate it as "guest-friend"; your ξένος was someone whom you could rely upon to provide hospitality, and to whom you were obliged to provide hospitality in return.
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