Green’s Dictionary of Slang

(orig. Aus./N.Z.) a bore, a loudmouth who refuses to stop talking.

c.1943		‘Bill O. Lading’ You Chirped a Chinful!! n.p.: Ear Banger: Extols merits to officers.
1946		R. Rivett Behind Bamboo 396/1: Ear basher, one who talks too much.
1955		D. Niland Shiralee 172: Not a bad old cow [...] but, hell, what an ear-basher.
1965		W. Dick Bunch of Ratbags 155: On top of this he was an ear-basher.
1976		M. Powell Down Under 130: He’s a proper old ear-basher when he gets started.
1983		J. Byrell (con. 1959) Up the Cross 76: Urgers, ear bashers and the like.