Green’s Dictionary of Slang

gabber n.¹

talk, loquacity.

1859, 1860		Hotten Dict. of Modern Sl. etc.
1864, 1867, 1870		Hotten Sl. Dict.
1895		Crowe Aus. Sl. Dict. 31: Gabber [...] foolish talking.
1915		Hull Dly Mail 2 Oct. 3/5: The combination of ‘gossip, gabber and gas,’ which we had dealt by penny dreadfuls.

In phrases

on the gabber (adj.)

talking away, talkative.

1930

Hull Daily Mail 22 Aug. 1/6: A young Hull husband [...] said that his wife was ‘always on the gabber’. The Stipendiary: ‘Whatever is that’. ‘She is always chewing the rag [...] arguing the point’.