'encephalous' originates from Greek, specifically the word 'enkephalos,' where 'en-' meant 'in' and 'kephalē' meant 'head.'

'enkephalos' was adopted into New Latin as 'encephalus,' and eventually became the modern English word 'encephalous.'

Initially, it meant 'having a brain (inside the head),' and this meaning has remained the same in modern usage.