makeweight

Something of inferior quality which is included in a shipment to make up the weight.

1893, Richard Le Gallienne, in a publisher's report on stories by Ernest Dowson, quoted in Jad Adams, Madder Music, Stronger Wine, page 88. I would advise you to accept these as an instalment of a volume, (they are not big enough to make one themselves) with the promise that the stories to come should be more striking, more original in theme — not less so, not mere makeweights — than those under consideration.

Something included to add to the apparent weight or force of an argument.

He added a long litany of peripheral precedents which the judge dismissed as mere makeweights.

Other railway schemes of the earliest period certainly mentioned benefits to agriculture, but only as a make-weight; most of them justified themselves by improved transport of minerals for shipment, […], or by carriage of bulk loads of manufactured goods.