'amyelencephalic' originates from Greek, specifically the word 'amyelos,' where 'a-' meant 'without' and 'myelos' meant 'marrow,' combined with 'encephalos' meaning 'brain.'

'amyelos' combined with 'encephalos' in Greek to form 'amyelencephalic,' which was adopted into English medical terminology.

Initially, it meant 'without marrow or brain,' and this meaning has largely remained the same in modern usage.