Green’s Dictionary of Slang

1. flattering.

1907		‘Blackbird and Woss-Woss’ in W. Jekyll Jam. Song and Story 24: The fellow so sweet-mout’ say in cross way ‘No’.
1934		J. Peterkin Roll, Jordan, Roll 103: But Harry, e too sweet-mouth! [...] Harry talk so promisin.
1979		T. Rhone Old Story Time 1 i: Sweet-mouth politician promise to bring down the moon.
1994		C. Cooper Female Sexuality in Lyrics of Bob Marley and Shabba Ranks 4: This is classic Jamaican sweet-mouth talk.

2. greedy, gluttonous.

1896		V. Heaven Jam. Proverbs n.p.: Sweet-mout fly follow coffin go a hole [DJE].
1907		W. Jekyll Jam. Song and Story 24: The fellow so sweet-mout’ [DJE].