codswallop, n. — Green’s Dictionary of Slang

codswallop n.

[ety. unknown; there is an implication of cods n.¹ (1), but no proven link. Linguistically cod n.² (3) + dial. wallop, to chatter, to scold is feasible, but the chronology may militate against it]

nonsense, rubbish, drivel; also attrib.

1959		Galton & Simpson ‘The Poetry Society’ Hancock’s Half-Hour [radio script] What a load of rubbish [...] I have never heard such unadulterated codswallop in my life.
1960		Galton & Simpson ‘The Reunion Party’ Hancock’s Half-Hour [TV script] What a load of codswallop.
1963		Radio Times 17 Oct. 52/2: Just branding a programme as ‘rubbish’, ‘tripe’, or – there are a lot of these – ‘codswallop’, gives little indication of what moved the viewer to write [OED].
1971		A. Buzo The Roy Murphy Show (1973) 106: What a load of childish codswallop!
1989		A. Higgins ‘The Bird I Fancied’ in Helsingør Station and Other Departures 200: A load of codswallop.
1991		M.B. ‘Chopper’ Read Chopper From The Inside 69: All white guys look alike! What a load of codswallop.
2004		M. Heatley John Peel 30: Talking a load of codswallop.
2009		L. McIlvanney All the Colours 13: [S]ome plausible codswallop.
2012		(con. 1943) G.S. Manson Coorparoo Blues [ebook] ‘Cut the codswallop, whattya want?’.
2023		R. Milward Man-Eating Typewriter 92: I detested the whole codswallop charade.