'august' originates from Latin, specifically the word 'augustus', where the root 'augere' meant 'to increase' (and 'augeo' meant 'to increase, to honor'), and 'augustus' carried the sense of 'consecrated' or 'venerable'.

'august' changed from Old French 'auguste' and Middle English 'august', and eventually became the modern English word 'august'.

Initially, it meant 'consecrated' or 'venerable', but over time it evolved into its current meaning of 'majestic, dignified' (and the comparative 'auguster' simply signals a greater degree of that quality).