Green’s Dictionary of Slang

1. in fig. use, one who has a ‘big mouth’, e.g. a braggart or an informer.

1910		Eve. Star (Wash., DC) 16 Oct. 76/8: This satchel-mouthed braggart infests the cafes and demands attention by abusing the waiters.
1917		H. Dickson Unpopular Hist. of the US 74: Immediately the War of 1812 broke out, satchel-mouthed patriots raised the cry of ‘On to Canada!’.
1925		H. Dickson Old-Fashioned Senator 55: His sympathy for people who cultivated their land never degenerated into the rantings of a satchel-mouthed demagogu.
1960		C. Cooper Jr Scene (1996) 122: Listen, you satchel-mouthed little punk.

2. used of someone who has a large mouth.

1971		T. Fielding Fielding’s Travel Guide to Europe 744: It is most famous for its pet pelicans — Peter and 2 or 3 cronies who back up his Satchel-mouthed Highness.
2003		G. Brownstein Curious Case of Benjamin Button 63: His hair was short and soft and shined with oils, his face chocolate and friendly and satchel-mouthed.