Green’s Dictionary of Slang

1. (US black) a confidence trickster.

1935

E. Freeman ‘The Whirling Hub’ in Afro-American (Baltimore, MD) 23 Mar. 15/1: Another [church trustee] was taken by the ducks for one hundred smackers.

2. (US black) an unpleasant or ugly person.

1987		Public Enemy ‘Miuzi Weighs a Ton’ 🎵 You know the ducks used to criticize my every phase of rapture.
1992		D. Burke Street Talk 2 37: She used ta be a real duck but now she’s too cold!

3. (US campus) a silly person.

1987

Eble Campus Sl. Oct. 2: duck – someone who is acting really stupid.