Green’s Dictionary of Slang

gum-beating n.

also gum-knocking
[gum beat v.]

(orig. US) incessant, frivolous, tedious chatter; also as adj.

[US] ‘Hectic Harlem’ in N.Y. Amsterdam News 8 Feb, sect. 2 n.p.: GUM BEATIN’. – Talking irrelevant and without fact [...] GUM KNOCKIN’ – Same.
[US]J.C. Monks Ribbon and Star 126: There was plenty of gum-beating that night [HDAS].
[US]F. Paley Rumble on the Docks (1955) 21: And he wasn’t like his mother, taking his father’s blows and gum-beating all the time.
[US]Mad mag. May 4: Enough gum-beating, Zark ... we’ve got to go find our rocket ship.
[UK](con. 1943) A. Myrer Big War 5: Now let’s not have any gum-beating about it.
[US](con. 1950) R. Leckie March to Glory (1962) 22: He had grinned to hear them grumble, for Barber knew that gum-beating Marines are hard to lick.
[US]R.C. Cruz Straight Outta Compton 17: Gum-beating. Going for soul. Giving out.