My nephews and I were holed up at the TWA Hotel in New York on a rainy Sunday a few weeks ago, waiting to attend an evening wedding. 

I fiddled with my phone and laptop and scanned the TV, while explaining that this was a big day for my fantasy football teams. (To be honest, every Sunday during the NFL season is big.)

Though the three teens knew a lot about football, I was taken aback when they said that unlike some 45 million Americans they had never learned the fantasy version — which has become a billion-dollar enterprise. So I told them the backstory.

It was a similarly rain-soaked weekend 61 years ago when Bill Winkenbach, an owner of the positively awful Oakland Raiders, flew into the TWA terminal for a Sunday game against the Titans (later the Jets). Depressed over his team’s 0-7 record and lack of promotable stars, he and some friends spent most of the night in a hotel bar, inventing a game that would allow them to roster stars of every team — players like Jim Brown, Mike Ditka and Frank Gifford.

Ten months later the Greater Oakland Professional Pigskin Prognosticators League (GOPPPL) held its first formal draft at Winkenback’s home. The league remained private until 1969 when one of the originals, Andy Mousalimas, opened the game to patrons at his sports bar, the King’s X.

What followed was explosive popularity that spread across the nation, with the biggest breakthrough coming in 1985 when Grandstand Sports launched the first internet-based fantasy platform. In 2010 the NFL got into the game and today most teams are investors in fantasy operations.

Conflicts are easy to find. This season, Jacksonville’s star running back Travis Etienne had a career game, then posted on social media: “I played against myself in fantasy fb today.”

While most fans like me play for token sums, fantasy football has grown into a high-stakes competition for sharps, who use sophisticated computer programs to set their lineups. DraftKings runs a contest dubbed The Milly-Maker, awarding a $1 million first prize each week of the NFL season.

Meanwhile, at our hotel, the boys and I formed TTWAHL (The TWA Hotel League) for which we each pick a weekly roster. In our first match, Alex scored a remarkable 151 points. Nick had 132, and Jake finished with 126.

As for me, I cautioned the guys that I’m what Yahoo calls a “veteran,” devoting many hours each week to digesting fantasy advice from people like NBC’s Matthew Berry, ESPN’s Field Yates and Al Zeidenfeld, who won a million dollars in 2016 and parlayed it into a touting empire on YouTube and ESPN.

I told them how miserable Bill Winkenback must have felt when the Raiders lost in the Manhattan mud and finished their season 1-13. My nephews were impressed by my knowledge until my score was posted. I got 67 points.

Peter Funt’s latest book is “Playing POTUS: The Power of America’s Acting Presidents,” about comedians who impersonated presidents.