the OED has chunter (chunner, chounter, chunder) as:

To mutter, murmur; to grumble, find fault, complain. Also in extended use.

1870 E. Peacock Ralf Skirl. II. 117 Th' capt'n went away chunterin'. 1921 D. H. Lawrence Sea & Sardinia iv. 135 A thin old woman+was chuntering her head off because it was her seat. 1949 C. Fry Lady's not for Burning 27 You+fog-blathering, Chin-chuntering, liturgical,+base old man! 1955 D. Barton Glorious Life i. 19 Paul's telephone rang.+ There was long chuntering on the wire. 1957 ‘N. Shute’ On Beach i. 2 The baby stirred, and started chuntering and making little whimpering noises. 1965 Spectator 5 Mar. 295/3 An old man+chunters a bit of folk tune which the solo horn dreamily perpetuates. 1968 Autocar 25 Jan. 27/2 The Herald ‘chunters’ straight across the road in front of us.

...so I guess it's used for most any sort of going on and on.

[M-W doesn't do chunter justice at all, having it simply as synonymous with mutter]

p.s. - Max, this one will show up in wwftd real soon.