late 15c., from French estrangier "to alienate," from Vulgar Latin *extraneare "to treat as a stranger," from Latin extraneus "foreign, from without" (see strange). Related: Estranged.

"not belonging or proper to a thing; not intrinsic or essential, though attached; foreign," 1630s, from Latin extraneus "external, strange," literally "that is without, from without" (as a noun, "a stranger"), from extra "outside of" (see extra-). A doublet of strange. Related: Extraneously.

late 14c., straunger, "unknown person, foreigner, one who comes from another country," 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."

By 15c. as "not a citizen of a nation, not a member of a religious group, craft, family, etc." The English noun never picked up the secondary sense of the adjective. Also from late 14c. as "traveler, transient," As a form of address to an unknown person, it is recorded from 1817, American English rural colloquial. The meaning "one who has stopped visiting" (often with reminder to not be one) is recorded from 1520s.

word-forming element meaning "outside; beyond the scope of; in addition to what is usual or expected," in classical Latin recorded only in extraordinarius, but more used in Medieval Latin and modern formations; it represents Latin extra (adv.) "on the outside, without, except," the old fem. ablative singular of exterus "outward, outside," comparative of ex "out of" (see ex-).