late 15th century: from French avarie ‘damage to ship or cargo’, earlier ‘customs duty’, from Italian avaria, from Arabic ‘awār ‘damage to goods’; the suffix -age is on the pattern of damage. Originally denoting a duty payable by the owner of goods to be shipped, the term later denoted the financial liability from goods lost or damaged at sea, and specifically the equitable apportionment of this between the owners of the vessel and of the cargo (late 16th century); this gave rise to the general sense of calculating the mean (mid 18th century)