'Southwestern' originates from the combination of 'south' and 'west', where 'south' meant 'toward the south' and 'west' meant 'toward the west'.

'South' and 'west' combined in Middle English to form 'southwest', and eventually became the modern English word 'Southwestern'.

Initially, it meant 'toward the southwest direction', but over time it evolved into its current meaning of 'situated in or coming from the southwest'.