'Hysteria' was once the name for an illness that was thought to be peculiar to women. Fainting, anxiety, strong emotion and insomnia were all thought to be indications that the lady in question was suffering from the complaint. The condition was considered real for a long time; the Ancient Greeks believed that a woman's uterus could become detached and move around her body, thus making her ill. From the Renaissance, a connection with sex was made, and until the 20th Century it was believed that the cure was 'pelvic massage' (use your imagination). Certain devices were invented to aid in this treatment, eventually entering the home appliance market. The advertisements for these products are amusing to look back on, as everything but their true purpose was emblazoned in proud copy; 'Vibration is Life' being a particular gem. Ladies might be pleased to know that these items were being sold to housewives around a decade before the electric iron and the vacuum cleaner.
Interest in hysteria was a prime concern when the practice of psychoanalysis was emerging; one of Sigmund Freud's books was called 'Studies on Hysteria'. Switzerland was the place where much of this early research and investigation was carried out, and consequently a number of clinics were established there, including the Rheinau-Zurich. The famous Swiss psychiatrist Paul Eugen Bleuler was Director there at one time.
As an illness, hysteria has been fully discredited for decades now. Earlier in this story, Carter describes the revenants of the town "torment[ing] pubescent girls with fainting fits, disorders of the blood, diseases of the imagination" which is extremely clever. These girls are not irrational; in the world of the story, we know there must be very real supernatural forces acting upon them.