 The term " plum cake " and " fruit cake " have become interchangeable . Since dried fruit is used as a <unk> agent and any dried fruit used to be described as " plums " , many plum cakes and plum puddings do not contain the plum fruit now known by that name . ( Plum pudding is a similar , <unk> dish prepared with similar ingredients , cooked by steaming the mixture rather than baking it . ) The term " plum " originally referred to prunes , raisins or grapes . Thus the so @-@ called plums from which English plum puddings are made " were always raisins , not the <unk> <unk> fruits that the name suggests today . " 
