The word mail means the armour material, not the armour made from it. A mail shirt is a hauberk, haubergeon, byrnie. Mail leggings are chausses, mail hoods are coif, and mail mittens are mitons. A mail collar hanging from a helmet is camail or aventail. A mail collar worn around the neck was called a pixane or standard.
"Mail" was invented by ancient Assyrians, a civilization in the Middle East that existed thousands of years ago. They sewed iron rings to leather coats to make better armor. As the Assyrians fought other civilizations, their armor was discovered and copied, until instead of sewing the rings to a coat, armor makers just linked the rings together into wearable clothing.
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