This mainly British colloquial expression — meaning nonsense — is recorded only from the 1960s, but is certainly older. Its origin is uncertain. Some argue it may be from cods, an old term for the testicles that derives from the Anglo-Saxon sense of cod, a bag. It is also suggested that wallop may be connected with the dialect term meaning to chatter or scold (not with the word meaning a heavy blow).
One explanation has it that it refers to the late Hiram Codd, who — despite his archetypally American first name — was British, born in Bury St Edmunds in Suffolk in 1838. He spent his life working in the soft drinks business. In the 1870s, he designed and patented a method of sealing a glass bottle by means of a ball in its neck, which the pressure of the gas in the fizzy drink forced against a rubber washer. Making the bottle was a technical challenge, since the ball necessarily had to be larger than the diameter of the neck. It was only in 1876, when he teamed up with a Yorkshire glass blower named Ben Rylands, that the answer was found. The Codd bottle was an immediate success; surviving examples are now highly collectable. You opened them by pushing the ball into the neck, and openers in the shape of short, thin cylinders were supplied for the purpose. One unexpected problem was that children smashed the bottles to use the glass balls as marbles.
The suggestion is that drinkers who preferred their tipple to have alcohol in it were dismissive of Mr Codd’s soft drinks. As beer was often called wallop, they referred sneeringly to the fizzy drink as Codd’s wallop, and the resulting word later spread its meaning to refer to anything considered to be rubbish.
This story reeks of the approach to word history called folk etymology. As one writer has put it, it seems rather too neat an explanation to be true. But nobody’s come up with anything better.