Green’s Dictionary of Slang

(US) empty, meaningless chatter.

1927		D. Hammett ‘The Big Knockover’ Story Omnibus (1966) 283: That’s probably a lot of chewing gum, but anyway this time the police will be ready.
1930		D. Hammett Maltese Falcon (1965) 414: He’ll be tickled pink to persuade himself that anything the punk tells him about it is a lot of chewing-gum.