'backswordmen' originates from English, specifically the compound of 'backsword' and 'man', where 'backsword' is formed from 'back' (Old English 'bæc' meaning 'back') + 'sword' (Old English 'sweord' meaning 'sword'), and 'man' comes from Old English 'mann' meaning 'person'.

'backsword' appeared in Early Modern English to denote a single-edged sword; 'backswordman' came to denote a person armed with such a weapon, and the plural follows the irregular Old English/Modern English pattern from 'man' to 'men', producing 'backswordmen'.

Initially it meant 'a man armed with a backsword'; over time the meaning has remained largely the same but the term is now chiefly historical or literary.