'onsite' originates from the combination of 'on' and 'site', where 'on' meant 'in a position above' and 'site' referred to 'a place or location'.

'onsite' evolved from the Middle English word 'site', which was derived from the Latin word 'situs', meaning 'position or location'.

Initially, it meant 'at the location', and this meaning has largely remained the same in modern usage.