1919, Tomáš Garrigue Masaryk, The Spirit of Russia: Studies in History, Literature and Philosophy, Volume 2, translated from German by Eden and Cedar Paul, page 298. In their endeavour to be a purely proletarian party they penalised the intelligentsia, and the more extreme and radical section among them even demanded that the party should become wholly a mass movement, for leadership, they said, was improper and must be abolished (must be "liquidated," whence this trend was called "liquidationism").
Source: wiktionary