'chainmail' is a compound of 'chain' and 'mail'. 'Chain' originates from Old French 'chaine', from Latin 'catena', where 'catena' meant 'chain'. 'Mail' originates from Old French 'maille', meaning 'mesh' or 'net' (used of armor as a mesh of rings).

'chain' came into English from Old French 'chaine' (via Middle English), and 'mail' came from Old French 'maille'. The compound (Middle English forms such as 'chaine-maille' or similar constructions) evolved into the Modern English 'chainmail'.

Initially used to describe a mesh-like armor made of interlinked rings, the meaning has largely remained the same in modern usage, though 'mail' alone and variants like 'chain mail' or 'chainmail' are used interchangeably.