1660s, "reference, relation, relationship," from French rapport "bearing, yield, produce; harmony, agreement, intercourse," back-formation from rapporter "bring back; refer to," from re- "again" (see re-) + apporter "to bring," from Latin apportare "to bring," from ad "to" (see ad-) + portare "to carry" (from PIE root *per- (2) "to lead, pass over")
Psychological meaning "intense harmonious accord," as between therapist and patient, is first attested 1894, though the word had been used in a very similar sense with reference to mesmerism from 1845 (first recorded in Poe). See also report (n.). Johnson frowns on the word and credits its use in English to Sir William Temple, naturalizer of French terms, who did use it but was not the first to do so.