'amnesiac' originates from Greek, specifically the word 'amnesiā,' where 'a-' meant 'not' and 'mnasthai' meant 'to remember.'

'amnesiā' transformed into the Latin word 'amnesia,' and eventually became the modern English word 'amnesiac' through Middle English.

Initially, it meant 'loss of memory,' and this meaning has largely remained the same in modern usage.