'metal-coated' originates from Modern English as a compound of 'metal' and 'coated'. 'metal' ultimately originates from Latin, specifically the word 'metallum', where 'metallum' meant 'mine' or 'metal'. 'coated' is derived from 'coat', which comes from Old English 'cote' meaning 'garment' or 'shelter'.

'metal' changed from Latin 'metallum' to Old French 'metal' and then to Middle English 'metal'; 'coat' developed from Old English 'cote' to Middle English 'cot(e)' and modern English 'coat'. The compound 'metal-coated' formed in Modern English by combining these elements.

Initially the roots referred to 'metal' and a 'garment/shelter', but over time 'coat' acquired the sense 'to cover (a surface)', so 'metal-coated' came to mean 'covered with a layer of metal'.