The Little Brown Jug is the oldest football trophy in all of college football, so naturally most of what you think about it isn't true. Michigan Coach Yost didn't really buy the jug out of fear Minnesota would try to poison their drinking water. Similarly Gophers Athletic Director Dr. Cooke probably never refused to return the jug to Yost, making him win it back.
To illustrate this let's look at the first known article about the jug, from February 7, 1904 in the Minneapolis Tribune:
Was Brought From Ann Arbor Filled With Michigan Water for Use of Wolverines During Football Game—Was Forgotten After Contest and Now Reposes In Dr. Cook's Office.
People wandering into the office of Dr. L. J. Cooke at the university gymnasium are attracted by a large white Jug, resting in a conspicuous place over the doorway. It is a trophy and last remembrance of the great game on Northrop field on Oct. 31, 1903. In short, it Is the Michigan water jug, which played so important a part in the great gridiron contest of that date.
The jug is two feet high and holds several gallons of water. It was brought to Minneapolis from Ann Arbor for use at the game on the side lines during that famous struggle. Whenever a Michigan man was hurt, the huge Jug was sought and fresh water poured from it into a small bottle to be carried onto the field by the trainer.
That the Jug did Its work well Is attested by the fact that only one Wolverine had to leave the game. Its life-giving contents of fresh spring water was a boon to the struggling players, especially after Minnesota got started on that famous march that resulted in the tieing of the score. In the excitement following the game the Michigan trainer lost his precious Jug and it was later found by a Minnesota man and carried to the gymnasium. It has a glossy coat of white paint on which has been inscribed the score: Minnesota 6: Michigan, 6, and other appropriate reminders of the fierce struggle. The Jug now occupies a prominent place In Dr. Cooke's office and will continue to beheld as a trophy as long as there is a Minnesota student who takes pride in recounting the famous gridiron battle in which It played its share.
Nothing is mentioned about Michigan wanting the jug back. The article was published a mere 4 months after the game and yet there are some clear inaccuracies. Most obvious is that the jug wasn't brought from Michigan, but in reality purchased for 30 cents at a Minneapolis store the day of the game. The last sentence essentially says the jug will stay in Dr. Cooke's office forever. There is an actual photo from 1905 that shows exactly where it was hung, this is about as cool as it gets.
Fast forward six years. The Gophers and Michigan had only played twice since the 1903 game. Michigan won both games and the jug made its way back to Ann Arbor. A publication unfortunately named Michiganensian published a story about the jug in 1910.
First the obvious. The thing isn't even brown! This article gets the story straight from Minnesota coach Doc. Williams who had also been with the Gophers back in 1903. Doc Williams stating they gave the jug back to Michigan because the "players stole it" is a new version of the story. Another weird lie in Doc Williams story is him saying that his players had carried it around all the time, which we know isn't true based on the 1904 Tribune article. So by 1910 the legend is already growing but not in any way we would recognize today.
Surprising is the lack of any mention of poison. Michigan's coach Fielding Yost's fear of Minnesota tainting the players water is the myth often told to justify the need for a jug in the first place. The blog Mvictors does a really great job debunking that. Suffice it to say that poison in the water was a later addition to spice up the story.
The only known photo from the 1903 Gophers - Wolverines game. Via MNHS.
Michigan didn't seem to miss the jug from 1903 when it was left at Minnesota until the two teams again played in 1909. Most likely Fielding Yost saw the jug in Cooke's office before the 1909 game and a plan was hatched to play for it. Again hat tip to Mvictors for the research on that one.
So when did the story start to get spiced up? The phrase "little brown jug" isn't used in newspapers until 1919. Whenever the hype machine started coming out with embellishments of the original story is unclear.
The 1903 game grossed $30,993.50 (the equivalent of $860,000 in todays scrilla), probably making clear to both Minnesota and Michigan early on that a well publicized rivalry was good financially for everyone.