Impose: lay on (in various uses); exert influence upon, as with fraudulent intent or effect: Latin imponere: place on or into, inflict, set over, lay as a burden, deceive, trick see POSE. Hence IMPOSING, exacting, impressive. So IMPOSITION: laying-on of hands (Wyclif Bible); impost [giving IMPOSTOR: one who imposes on others]; exercise imposed as a punishment”
(The Oxford Dictionary of English Etymology)
Writing is a curious imposition: a burden and a trick, an exercise imposed upon impostors as a punishment. It is a laying-on of hands, an attempt to heal the breach, to close the wound, to exorcise and expiate.