The term shaggy dog story dates from the 1930s, though shaggy dog stories were told long before then. We will look at the definition of a shaggy dog story, where the term comes from and some examples of its use in sentences.
A shaggy dog story is a long joke full of twists and turns and irrelevant details that ends in a anti-climatic punchline or a pun. The humor in a shaggy dog story is derived from the listener’s expectation that all the details will have some meaning at the end of the story, when in fact, they are merely red herrings. Mark Twain is famous for the shaggy dog story form, though he never referred to such stories in this way. The name shaggy dog story didn’t appear until the 1930s, probably because the first story identified as such involved a dog that was shaggy. There is some dispute as to which story was the first joke labeled a shaggy dog story, though it is generally agreed that the story involved a long treatise on the shagginess of a particular dog that was finally entered into a contest for shaggy dogs, only to be told by a judge at the end of the story, “That dog isn’t so shaggy.” The Oxford English Dictionary prefers the term to be hyphenated, as in shaggy-dog story, but it is more commonly seen without the hyphen.
From there, the story becomes much more than the subgenre of a shaggy-dog story, although a shaggy dog is literally at its heart. (The Columbus Dispatch)
This can work wonders when she’s telling an absurd shaggy dog story like her routine about the “No Moleste” signs on Mexican hotel room doors, but it’s an absolutely perfect fit for something as fiercely grief-stricken as One Mississippi. (The Guardian)