stranger (n.)

late 14c., "unknown person, foreigner," from strange + -er (1) or else from Old French estrangier "foreigner" (Modern French étranger), from estrange. Latin used the adjective extraneus as a noun to mean "stranger." The English noun never picked up the secondary sense of the adjective. As a form of address to an unknown person, it is recorded from 1817, American English rural colloquial. Meaning "one who has stopped visiting" is recorded from 1520s.