'fetus' originates from Latin, specifically the word 'fētus', where 'fētus' meant 'offspring' or 'bringing forth'.

'fētus' changed from the Latin word 'fētus' and eventually became the modern English word 'fetus'.

Initially, it meant 'offspring' or 'bringing forth', but over time it evolved into its current meaning of 'an unborn offspring of a mammal'.