E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A ruffian; a swaggerer. From swashing, says Fuller, and making a noise on the buckler. The sword-players used to swash or tap their shield, as fencers tap their foot upon the ground when they attack. (Worthies of England.) (A.D. 1662.) (See SWINGE-BUCKLER.)
A bravo, a swashbuckler, one that for money and good cheere will follow any man to defend him; but if any danger come, he runs away the first, and leaves him in the lurch.Florio.