"one who scientifically treats or studies mental illness," 1864, from French aliéniste, from alienation in the sense of "insanity, loss of mental faculty," from Latin alienare "deprive of reason, drive mad," literally "to make another's, estrange" (see alienate). The mental sense of alienate has since mostly died out in English, but Middle English had aliened from mind "deranged, not rational" (late 14c.), and alienation was used from 15c. in a sense of "loss or derangement of mental faculties, insanity."
updated on September 16, 2022