Green’s Dictionary of Slang

(W.I.) a gossip, a chatterbox; also as adj.

1942		L. Bennett ‘Street Crier’ in Jamaica Dialect Verses 3: Yuh know mouty-mouty Dinah? [...] She go tell Tayma pickney fadah, / Miss Imo nephew you know?
1957		F.G. Cassidy ‘Iteration as a Word-forming Device in Jamaican Folk Speech’ in AS XXXII:1 51: mouty-mouty, mouthy, impertinent.
1966		(ref. to 1940s) L. Bennett Jamaica Labrish 223: mouty-mouty. given to gossip.
1968		B.L. Bailey Jam. Creole Lang. Course 143: Him stare eena har face an seh, ‘Thou art de mouti-mouti!’.