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In all the words currently being written about the end of the Bill Belichick era in Boston — or, technically, the Boston suburbs — which reportedly finally came to a close on Jan. 11 after weeks of speculation, the end of the N.F.L. season and the Patriots’ dismal loss to the Jets, the one that sticks in my mind is “hoodie.”

More than anyone except perhaps Mark Zuckerberg, Boston’s famous football coach has become synonymous with that particular garment. It is “an inseparable part of his legacy,” according to Bleacher Report. His “trademark,” wrote Sports Illustrated. “Iconic,” crowed Buzzfeed. For decades the hoodie helped burnish the Belichick legend, but recently it has begun to seem part of the problem: less a symbol of his coaching genius than, perhaps, a sign of his obsolescence.

For most of his 24 years with the Patriots, the sweatshirt has been Mr. Belichick’s garment of choice for game day. And not just any old sweatshirt, but a particularly nondescript, schlubby blue or gray sweatshirt, often with the sleeves lopped off in a seemingly random way somewhere between the elbow and the shoulder, and layered over another shirt. Sometimes it was paired with flip-flops. The majority of that time, when he was leading the team to its six Super Bowl wins, the sweatshirt seemed to symbolize Mr. Belichick’s singularity: his ornery refusal to be anything but himself or follow any vision but his own; his gruff, blue-collar fighting spirit; his consistency; his refusal to give up — not the game and not his favorite wardrobe item.

It got him named to various “best-dressed” lists with the sort of affectionate irony traditionally lavished on irascible but beloved uncles, and led to a “Bill Belichick raglan pullover hoodie” being sold in the N.F.L. merch shop. His commitment to the garment inspired one football prognosticator to create a “hoodie tracker,” and it has been the subject of Super Bowl betting. Mr. Belichick even presented a hoodie to President George W. Bush on a visit to the White House.

The origin story of Mr. Belichick and the sweatshirts is part of his mystique. He first appeared in a gray hoodie in 2003. (Before that he often wore windbreakers on the field.) As the tale goes, he adopted the hoodies after the N.F.L. made a deal with Reebok (now Nike) that included coaches, meaning that they were forbidden to wear the sort of tailored suits that once distinguished men like Tom Landry, Hank Stram, Blanton Collier and even Vince Lombardi. Instead they had to wear team gear, becoming a walking billboard for the sponsor.