sweetmouth, n. — Green’s Dictionary of Slang

sweetmouth n.

(W.I.)

1. (also sweet-mouth man) a flatterer, a persuasive person.

1934		J. Peterkin Roll, Jordan, Roll 105: Harry is a deceitful sweet-mouth man.
1994		M. Montague Dread Culture 36: Sweet mout. Yuh gwine give all di girls in Toronto heartache.

2. flattery, persuasiveness.

1959

A. Salkey Quality of Violence (1978) 147: There’s no use your trying to put ‘sweet mouth’ on any of us.

talk sweetmouth (v.)

to talk ingratiatingly.

1922		(con. mid-19C) A. Gonzales Black Border 139: No suh! You lub fuh talk sweetmout’ talk ’long’um, but you dat stingy you nebbuh buy uh candy!
1925		Du Bose Heyward Porgy (1945) 43: Ain’ yuh ’shame’ tuh set dey befo’ me, and talk sweetmouth ’bout dat murderin’ Crown’s Bess?