Green’s Dictionary of Slang

slabber v.

(Irish) to talk, esp. nonsense.

[Ire]Spirit of Irish Wit 221: Ye slabber up wickedness as if it was buttermilk or bonnaugh clabber.
Sth Wales Dly News 24 May 2/6: A Slabbering Compliment. Our contemporary the Western Mail [...] has thought fit to pay us a back-handed compliment.
[UK]Surrey Mirror 7 June 6/5: Mr Barnes [...] denounced all the members [...] as ‘slabbering idiots’.
[Ire](con. 1945) S. McAughtry Touch and Go 160: Let him slabber away there.