In marine Insurance. There is considerable analogy between ballast and dunnage. The former is used for trlmming-the ship, and bringing it down to a draft of water proper and safe for sailing. Dunnage-is placed under the cargo to keep it from be-ing wetted by water getting into the hold, or between the different parcels to keep them from bruising and injurlng each other. Great western Ins. Co. v. Thwlng, 13 walk 674, 20 L. Ed. 607
Source: Black's Law Dictionary 2nd Ed (1910)