'nonplated' originates from the combination of the prefix 'non-' (from Latin 'non', where 'non' meant 'not') and the adjective 'plated' from 'plate' (from Old French 'plate', ultimately from Late Latin 'platta'/'plata', meaning 'a flat object' or 'metal plate').

'plate' changed from Old French 'plate' (from Medieval/ Late Latin 'platta'/'plata') and became the Middle English word 'plate'; the negative prefix 'non-' was borrowed from Latin and became productive in English to form compounds like 'nonplated'.

Initially, 'plate' referred to a flat piece or metal plate; over time 'plated' came to mean 'covered with a metal layer', and 'nonplated' straightforwardly took the opposite sense 'not plated' without major semantic shift.