'easterly' originates from Old English, specifically the word 'ēasterlic,' where 'ēast' meant 'east' and '-lic' was a suffix meaning 'like' or 'pertaining to.'

'ēasterlic' transformed into the Middle English word 'easterly,' and eventually became the modern English word 'easterly.'

Initially, it meant 'pertaining to the east,' and this meaning has largely remained the same in modern usage.