A braggart. One who is very valiant with his tongue, but a great coward at heart. A barking dog that bites not. The character is from Spenser's Faërie Queene, and a type of the “Intemperance of the Tongue.” After a time, like the jackdaw in borrowed plumes, Braggadochio is stripped of all his “glories”: his shield is claimed by Sir Marinel; his lady is proved by the golden girdle to be the false Florimel; his horse is claimed by Sir Guyon; Talus shaves off his beard and scourges his squire; and the pretender sneaks off amidst the jeers of everyone. It is thought that the poet had Felipe of Spain in his eye when he drew this character.
(Faërie Queene, iii. 8, 10; v. 3.)
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894