'relay' originates from French, specifically the verb 'relayer,' where the prefix 're-' meant 'again' and the root suggested 'to place or leave (for rest or relief).'

'relay' entered Middle English from Old French (noun) 'relai'/'relais' meaning 'a place for change or rest' (for horses or messengers) and from the verb 'relayer'; it later developed into the modern English verb and noun 'relay.'

Initially, it meant 'to provide relief or a place for rest (especially for horses and messengers)'; over time it broadened to mean 'to pass on or transmit (messages, signals) and to replace or relieve someone in duty.'