Green’s Dictionary of Slang

a thug, a hired assassin.

1598		J. Sylvester Du Bartas II iii IV (1641) 187/1: Ador’d of Flatterers, Of Softlings, Wantons, Braves and Loyterers.
1611		Coryat Crudities 275: There are certaine desperate and resolute villaines in Venice called Braves.
1649		Milton Eikon 25: Happy times, when Braves and Hacksters were thought the fittest to defend the King.
1675		Dryden Aurengz I i 96: Morat’s too insolent, too much a Brave.
1681		W. Robertson Phraseologia Generalis 277/2: A Brave; (fellow hired to revenge a quarrel of another;) Sicarius percussor.
1822		R. Nares Gloss. (1888) I 105: brave. s. A bravado.