1912, in the meaning defined above
partial translation of German Abreagieren, noun use of abreagieren "to release or express (an emotion previously repressed or forgotten)," from ab "down, from" (going back to Old High German aba) + reagieren "to react," borrowed from French réagir, borrowed (with adaptation to agir "to act, take effect") from New Latin reagere — more at of entry 1, react