'passing' originates from Old French, specifically the word 'passer', where the root 'pass-' meant 'to go or move past'.

'passing' changed from Old French 'passer' and Middle English forms (e.g. 'passingen') and eventually became the modern English word 'passing'.

Initially, it meant 'to go by or move past', but over time it evolved to include the euphemistic sense 'to die' and senses relating to temporary occurrences or transfers.