Are you sure? Here's what I found on the McBain Gaelic Dictionary:
brag (Lewis), a sudden creeking noise, Norse brak. bragaireachd vain boasting, Irish bragáireachd, from bragaire, boaster; from the English brag. bragh an explosion, peal, Old Irish braigim, pedo; Latin fragor, crash, fragare, English fragrant. See bram. bràghad neck, throat, Irish bráighid, Old Irish bráge, g. brágat, Welsh breuant, Old Breton brehant, *brâgn@.t-; English craw, German kragen, collar, Middle High German krage, neck; Greek @Gbróghos, windpipe, English bronchitis. Bezzenberger (Stokes' Dict.), refers it ot the root of Norse barki, weazand, Greek @Gfárugx, English pharynx. bràghad is really the gen. of bràighe. bragsaidh braxy; from Scottish, English braxy.
They all sort of look like they might have a Germanic origin ...just wondering what your sources are?