'anencephaly' originates from New Latin and Greek, specifically the New Latin word 'anencephalus' which comes from Greek elements 'an-' + 'enkephalos', where 'an-' meant 'without' and 'enkephalos' meant 'brain' (literally 'in the head').

'anencephaly' changed from the Greek word 'anenképhalos' to the New Latin 'anencephalus' and eventually became the modern English word 'anencephaly'.

Initially, it meant 'without a brain' (literally 'lacking the brain'), and over time it has been used medically to denote the congenital condition characterized by absence of major parts of the brain and skull.