swashbuckle: [19] Swashbuckle is a backformation from swashbuckler [16], which originally denoted a warrior who struck his shield with his sword as a sign of aggression and machismo, rather like a gorilla beating its chest. It was a compound formed from swash ‘hit’ [16], a word of imitative origin which is now restricted to the sound of water splashing against a surface, and buckler ‘shield’. It was used broadly for a ‘swaggering fellow’, but the word’s modern associations of romantic swordplay and high adventure did not begin to emerge until the early 19th century.
