'swashbuckler' originates from English, specifically the combination of 'swash' and 'buckler', where 'swash' meant 'to strike or make a noise by striking' and 'buckler' meant 'a small round shield'.

'swashbuckler' formed in Early Modern English (16th–17th century) often written as 'swash-buckler' (a person who 'swashes' — strikes loudly — with a 'buckler') and later became the single word 'swashbuckler' in modern English.

Initially it referred literally to someone who made a loud striking noise with a small shield (a swaggering fighter); over time it evolved to mean a flamboyant, daring adventurer or romantic hero in fiction and popular usage.