Green’s Dictionary of Slang

1. to chatter.

1936		L. Dent ‘Angelfish’ in Goulart (1967) 249: Do you have to stand there and gobble at me?
1949		R. Chandler Little Sister 244: Don’t stall around or gobble about your income tax.

2. to talk incoherently.

1942

R. Chandler High Window 213: ‘And I know she didn’t push anybody out of any window. Does that explain matters?’ He gobbled, but nothing came that was coherent.