1866, "to confine within set limits," from French interner "send to the interior, confine," from Middle French interne "inner, internal," from Latin internus "within, internal" (see internal; also compare intern, n.).

1879, American English, "one working under supervision as part of professional training," especially "doctor in training in a hospital," from French interne "assistant doctor," literally "resident within a school," from Middle French interne "internal" (see intern, v.). The verb in this sense is attested from 1933. Related: Interned; interning.