1570s, from Fr. bragard (16c.), with pejorative ending (see -ard) + M.Fr. braguer "to flaunt, brag," perhaps originally "to show off clothes, especially breeches," from brague "breeches" (see bracket). There may be an element of codpiece-flaunting
in all this. The word in English at least has been influenced by brag, even if, as some claim, it is unrelated to it.