catharsis (n.)
1803, "bodily purging," from Latinized form of Greek katharsis "purging, cleansing," from stem of kathairein "to purify, purge," from katharos "pure, clear of dirt, clean, spotless; open, free; clear of shame or guilt; purified" (with most of the extended senses now found in Modern English clear, clean, pure), which is of unknown origin. Originally medical in English; of emotions from 1872; psychotherapy sense first recorded 1909, in Brill's translation of Freud.