Emily Dickinson Lexicon

AV'ER-AGE, n. [Norm. aver, avers, cattle, money, goods, Sp. averio, from aver or haber, Fr. avoir, to have or possess. In ancient law, a duty or service which a tenant was bound to render to his lord, by his beasts and carriages or instruments of husbandry. Spelman. But averagium signifies also the loss of goods in transportation; Sp. averia, damage sustained by goods or ships; Port. avaria, an allowance out of freight to the master of a ship, for damage sustained; contribution by insurers, to make good a loss; It. avaria; Dan. haverie, damage of a ship or waste of goods, extraordinary charges during a voyage. If avaria signifies damage, and is from aver or haber, Spanish, to have, the sense of the word is probably that which happens or falls, a misfortune, for the verb have and happen are radically the same word; Spanish, haber, to have, and to happen or befall; also fortune, property. This would give the sense of damage, or of proportion, lot, share, that which falls to each of a number. But the primary sense is not very obvious.]

1. In commerce, a contribution to a general loss. When for the safety of a ship in distress any destruction of property is incurred, either by cutting away the masts, throwing goods overboard, or other means, all persons who have goods on board, or property in the ship, contribute to the loss according to their average, that is, the goods of each on board. This principle, introduced into the commerce of Europe from the Rhodian laws, and recognized by the regulations of Wisby, is now an established rule in the maritime laws of Europe; for it is most reasonable, that when one man's property is sacrificed to save a ship, all persons whose property is saved, or in like hazard, should bear their proportion of the loss. – Spelman. Park. Beawes.
2. From the practice of contributing to bear losses, in proportion to each man's property, this word has obtained the present popular sense, which is, that of a mean proportion, medial sum or quantity, made out of unequal sums or quantities. Thus, if A loses 5 dollars, B 9, and C 16, the sum is 30, and the average 10.
3. A small duty payable by the shippers of goods, to the master of the ship, over and above the freight, for his care of the goods. Hence the expression in bills of lading, “paying so much freight, with primage and average accustomed.” – Cowel. Encyc.
4. In England, the breaking up of cornfields, eddish or roughings. Ash. Spelman. Upon, or on an average, is taking the mean of unequal numbers or quantities.