'almagest' originates from Arabic, specifically the word 'al-majisṭī', where 'al-' meant 'the' and 'majisṭī' referred to 'the greatest'.

'al-majisṭī' transformed into the medieval Latin word 'almagestum', and eventually became the modern English word 'almagest'.

Initially, it meant 'the greatest compilation', but over time it evolved into its current meaning of 'a comprehensive treatise on astronomy and mathematics'.