'passenger' originates from Old French, specifically the word 'passager', where 'passer' meant 'to pass'.

'passager' passed into Middle English as 'passager' (also spelled 'passenger') and eventually became the modern English word 'passenger'.

Initially it meant 'one who passes' or 'one who goes by/through'; over time it evolved into the more specific meaning 'a person who travels in a vehicle (not the driver)'.