Definition of "chain mail"

Chain mail is formed by a number of iron rings, each ring having four others inserted into it, the whole exhibiting a kind of net work, with circular meshes, every ring separately rivetted; this kind of mail answers to that worn on the ancient breast plates, whence they were denominated loricæ hammatæ, from the rings being hooked together.

1786, Francis Grose, A Treatise on Ancient Armour and Weapons, page 11