'backswordsman' originates from English, specifically the compound 'backsword' + the agentive suffix '-man', where 'backsword' meant 'a single-edged sword with a reinforced back' and '-man' meant 'person who uses or works with'.

'backsword' itself developed in late Middle/early Modern English from the elements 'back' + 'sword' (Old English 'bæc' and 'sweord'); the agentive form 'backswordsman' arose in early modern usage to denote a fighter or infantryman armed with such a weapon.

Initially it meant 'a fighter or soldier armed with a backsword'; that core meaning has largely remained, though the term is now rare or archaic.