'headache' originates from Old English, specifically the word 'hēafodæce,' where 'hēafod' meant 'head' and 'æce' meant 'pain.'

'hēafodæce' transformed into the Middle English word 'hedeake,' and eventually became the modern English word 'headache.'

Initially, it meant 'pain in the head,' and this meaning has largely remained the same in modern usage.