The dive went deep into the archives, uncovering years of history and years of disappointments, sneaking through the 1970s and '50s and '30s and, somehow, landing on the 1924-25 season. That was the key to the whole thing.
It was the first year of the Bruins. It was the year after the Canadiens won their first Stanley Cup as part of the National Hockey League.
It just made sense.
Both teams found their inspiration there, the key elements that would be transferred to the threads and stitches, the colors and collars of their Winter Classic jerseys, sweaters that both teams think symbolize where they've been and who they are. These are the jerseys that will be worn New Year's Day when the teams play in the annual outdoor event, this time at Gillette Stadium.
"It makes you realize how long this franchise has been going for, how many years, how many players have been through it, through the doors," the Bruins' Patrice Bergeron said. "Just makes you appreciate it even more."
From nearly the first moment that the teams for the Winter Classic are announced, the Reebok designers are at work, taking their cues from the teams' management, narrowing their suggestions into variations that are then approved by the teams, managing to coordinate uniforms that will be distinct, yet will be visually appealing together — and will look good from a distance.
It was how the Bruins ended up with their original crest, a bear in brown with the words "Boston" above and "Bruins" below with yellow arm stripes, all on a black background.
"We try and really dig into the team and franchise history, meaningful eras in the franchise and the design markers and elements that can make this jersey unique," Reebok lead designer Dominique Fillion said. "There's always a great story behind the jersey that we build and the reasoning of how the jersey came about."
It was the "Boston" that was crucial, something that Fillion called "very powerful and definitely strong and something that the team and the players would be very proud of wearing that game."
That's the point, really, to take emotion, pride, and history, and distill them into a mass of fabric, colors, and crests.
"Playing another Original Six [team] played a factor," Bruins president Cam Neely said, of the jersey design. "I wanted to go back further into our history and see what other options there were. I think it kind of made sense to look at the original jersey and try and take something from that.
"I love the history with what's happened over the years, not just the players that have played here, but also the uniform and different changes. I think it's pretty special to be part of an Original Six team, so having an opportunity to create something is kind of cool."
There are echoes of the Bruins' current third jersey in their Winter Classic sweater, the bear across the front, the team name overlay, the arm stripes. The Bruins opted for black rather than brown for the uniform.
"I love black," Neely said. "Then the crest itself was very unusual with the bear, a little different flavor with the bear plus the material. So just something I don't think our fans have really seen, especially in a long, long time. I thought it was a unique logo for us to use."
The Canadiens, too, went all the way back to that common year of 1924-25. They had combed through their archives, courtesy of in-house historian Carl Lavigne, wanting to find a story. They — like the Bruins — didn't just want this to be a well-designed jersey. They wanted it to say something.
"This was the year where the team was coming off its first Stanley Cup won as part of the NHL  and ownership decided to mark this by wearing a jersey with a globe design with the words Champions at the bottom, in honour of the 1924 World Champions," Canadiens executive vice president and COO Kevin Gilmore wrote in an e-mail.
"The year we wore this jersey also marked the Bruins' first season in the NHL so this is the year where the great rivalry started."
Montreal used that jersey as a starting point, inverting the shoulder logo with the chest logo, using a white C surrounding a red H and a globe on the arms. The arm stripes the Canadiens pulled from a jersey worn in the 1945-46 season by the likes of Maurice Richard on a team that beat the Bruins to win its sixth Stanley Cup.
As P.K. Subban told reporters when the jersey was unveiled, "It's not just a jersey, in my opinion, it's a symbol of what it means to be a Montreal Canadien."
So, yes, the rivalry is written in the stitching and coloring, the choices and decisions of the uniforms that will be donned in the dressing rooms of Gillette Stadium on New Year's Day.
"It was important for us that the jersey not only symbolize this great rivalry, but also speak to its history," Gilmore wrote. "From a players' standpoint, they all understand the significance of this great rivalry, but we hope that the inspiration for this design, one that touches on legendary teams and players that came before them, adds to this experience for them."