Entry revised for OED Online

Also cod's wallop. [Origin unknown.
It is often suggested that this word is < the genitive of the name of Hiram Codd (1838-87 ), British soft drinks manufacturer, who patented several designs for mineral water bottles in the 1870s + WALLOP n. (see sense 4c at that entry), and that it was originally used by beer drinkers as a derogatory term for soft drink. However, no evidence has been found for early use of the word in this sense, and derivation from the surname is not supported by early spellings.] 

    Nonsense, drivel.
 
   1959 R. GALTON & A. SIMPSON Best of Hancock (1986) 28 Tony. I was not. Sidney. Don't give me that old codswallop. You were counting your money. 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. 1966 J. PORTER Sour Cream vi. 72 It had all seemed a load of old cod's wallop to me at the time, but those lecturers were experts. 1966 A. PRIOR Operators vi. 64 All that stuff about mutual respect between police and criminal was a load of old codswallop. 1970 Peace News 30 Jan. 6/1, I hope you will stop publishing cod's wallop of the type which appeared..in Roger Moody's article.