The meaning and origin of the expression: Shaggy dog story

Shaggy dog story

What's the origin of the phrase 'Shaggy dog story'?

This appears to be an American phrase. The first mention of 'shaggy dog story' in print that I can find is in Esquire magazine, May 1937:

"One of the more sporting ways of finding out which ones are not [sane] is to try shaggy-dog stories on them."

Why the phrase 'shaggy dog story' was coined is difficult to determine. Presumably, it derives from an actual but improbable story about a shaggy dog. There are a few contenders for the honour of being the first such story.

For my money the one that is the most likely source of the phrase originates from the pen of the American author, dog breeder and journalist - Albert Payson Terhune. He was quite a celebrated author of animal stories, especially dog stories, in the early years of the 20th century. Terhune's best-known creation was Lad, the collie dog that took the lead, so to speak, in several popular books (and later a film), including his 1919 story Lad: A Dog. The later canine star Lassie is clearly modelled on Lad, who in Lad: A Dog tackles a poisonous snake, saves a crippled child and prevents the family barn from being burned down.

On 6th November 1926 the Canadian paper The Manitoba Free Press printed a piece by Terhune, which he wrote as if it were a true account of a dog called Lad – who is described in the text as a ‘shaggy dog’. The tediously detailed and meandering story certainly fits the bill of 'shaggy dog story', in that it requires us to believe that the hero survived shooting, clubbing and burial and came bounding back for more. The account is of a stray collie that was shot for killing sheep and which the author claims it to be 'true in all but details'. It is headed The Strangest Dog Story I Know:

"I tied Lad to a tree" he said, "with a lot of good stout wire. Then I shot him three times in the head, at close range. Then I hammered his head with a club. Then I dug a grave two feet deep and buried him. He didn't suffer, though. He never moved after the first shot hit him."...

"Imagine my astonishment, Sunday morning, three days later, when my little son rushed into my room, shouting:
'Dad, Laddie has come back. He still has the wire around him and there's a big hole in his neck! And he's all covered with earth.' There the dog stood on the front porch."...