A year ago, as the Baltimore Ravens under coach John Harbaugh and San Francisco 49ers under coach Jim Harbaugh advanced through the NFL playoffs, there was talk of a potential brother-vs-brother Super Bowl – a “Harbowl,” as some sportswriters had begun calling it.

Roy Fox of Pendleton, Indiana, is an ordinary football fan who had an idea: make T-shirts and hats with the word “Harbowl” on them, and sell them for some extra cash in case these brothers did ever meet up in a future Super Bowl. Mr. Fox remembered how Lakers Coach Pat Riley famously made money by trademarking the term “Three-Peat,” Fox told me this week, and so he decided to trademark “Harbowl” and “Harbaughbowl.”

So, is Mr. Fox expecting a payday this month, as the Harbowl becomes reality? Nope. NFL lawyers, threatening costly legal battles, pressured Mr. Fox to abandon his trademark. And under threat of costly court costs, Mr. Fox gave up the trademark early this season.

Here’s the story as told by Mr. Fox, federal trademark filings, and emails Mr. Fox forwarded to me:

Mr. Fox, figuring last year that the Harbowl might happen some day, signed up with the online legal services business Legal Zoom, and went through the process of applying for a trademark on both Harbowl and Harbaughbowl.

The USPTO processed Fox’s trademark application in February. In July, the PTO published the trademark request, as is standard, in order to see if anyone opposed it.

Resistance came from the NFL, famous for its zealous protection of its trademarks and its content. (Notice how many ads refer to “the big game” because they haven’t paid the NFL for the right to say “Super Bowl.)

First, in August, the NFL got the PTO to extend the period allowed for filing an objection. At the same time, the NFL wrote Mr. Fox, saying “We are concerned that, because our mark” that is, the words Super Bowl, “and your applied-for marks are similar, it may cause the public to mistakenly believe that your goods and/or services are authorized or sponsored by or are somehow affiliated with the NFL or its Member Clubs.”

In other words, if Mr. Fox sold a shirt saying “Harbowl,” the NFL was worried Fox’s customers would be duped into thinking they were buying official NFL merchandise. The NFL requested more information from Mr. Fox.

Over the course of August, NFL lawyers pushed Mr. Fox to abandon his trademark application. Mr. Fox didn’t want to abandon it. So the NFL pushed harder.

“If you are still interested in resolving this matter amicably and abandoning your trademark application, please contact me as soon as possible,” NFL Assistant Counsel Delores DiBella wrote to Mr. Fox in October. She warned that otherwise, the NFL “will be forced to file an opposition proceeding and to seek the recoupment of our costs from you.”

“I was threatened to be taken to court,” Fox told me, “and I just assumed I would lose, and I couldn’t afford the court costs.”

Mr. Fox is not a businessman or a lawyer. He says, “I didn’t know my rights.” He didn’t want to fight a costly legal battle with the NFL, and so he made a humble request: he would abandon his trademark in exchange for some Colts tickets. The NFL said no, according to Mr. Fox.

The NFL was helpful in one regard: “They were real, real cooperative on helping me abandon the trademarks,” Fox told me. He filed that abandonment in October. Three months later, the Harbowl became a reality, even if Mr. Fox’s business idea never did.

CORRECTION (1/24/13 at 1:35 pm: I accidentally typed “copyright” once when I meant “trademark.” I’ve fixed it.