For the next five hours, in windy, chilly conditions that worsened over the afternoon, Kennedy gamely kept playing. And playing. At one point, six of her grandchildren — she now has 35, plus one great-grandchild — rushed out to hug her. On the ninth hole, a band played “The Best Is Yet to Come” in her honor. On the 16th, Kennedy sank a lengthy putt to give her team one of its rare birdies for the day.

Walking to the next hole, she quipped, “Am I going to have to save us again?”

Farrelly, who’d met Kennedy for the first time the night before, at a gala dinner at her oceanfront home near the golf club, was still grinning after the round ended.

“My humor runs to raunchy, but there wasn’t much I said that could shock her,” he said. “She may be a legend and icon, but Ethel’s a cool chick, too, very young at heart.”

A cool chick, at 84. And now, a movie star.

On Thursday night, HBO will broadcast “Ethel ,” a 95-minute documentary by Rory Kennedy, 43, the youngest of her 11 children. The film premiered at January’s Sundance Film Festival and was shown earlier this fall at the JFK Library, where both Kennedys were on hand to discuss the project.

However, this week marks the first time a national audience will see and hear from an Ethel Kennedy who’s been largely out of public view for four decades. Before the film’s release, it had been at least 25 years since her last on-the-record interview. As she inches her way back into the limelight, albeit with some reluctance, viewers will get to see one of Camelot’s last surviving members, up close and in her twilight years.

The film’s focus is on Ethel Skakel Kennedy’s relationship with Robert F. Kennedy, her late husband, and the pivotal role she played in his public and private life. Narrated by Rory, “Ethel” contains previously unseen footage of its subject as a young bride, competitive athlete, campaign trail stalwart, world traveler, single mom, and eyewitness to history.

Eight of her surviving children — David, 28, died of a drug overdose in 1984; Michael, 39, was killed in a 1997 skiing accident — talk about their mother as “a force of nature in her own right,” as Kathleen Kennedy Townsend puts it, before and after their father’s assassination in 1968. Townsend, 61, is the oldest of 11 and currently chairs a Maryland-based nonprofit backing Democratic candidates and causes.

Kerry Kennedy, 53, president of the RFK Center for Justice and Human Rights, founded by her mother 44 years ago, recalls how, after their father died, it was Ethel who taught them sports, quizzed them on world affairs around the dinner table, dispatched them to live and work in foreign cultures, and steered them toward social justice causes like fighting poverty and promoting workers’ rights.

The film does not dwell long or often on personal tragedy or family scandal — part of her life story, too. “Why should I have to answer all these questions?” Ethel says irritably during a filmed conversation with Rory. Later, in a rare moment of somber self-reflection, she concedes she’s “had a lot of loss” over the years. But, she adds, “Nobody gets a free ride.”

Sheila Nevins, president of HBO Documentary Films, began encouraging Rory to make such a film years ago, she says, realizing that some topics would be skirted — or avoided altogether. Neither Kennedy seemed eager to proceed, according to Nevins, until 2009, when Ethel finally sold Hickory Hill, the family estate in McLean, Va., where she and Bobby raised their kids.

Ethel, a fierce competitor in everything from golf to board games, “was determined to win it” should a biographical film be made, said Nevins. “And she did.”

With Rory beside her, Ethel Kennedy sat for a pre-screening interview at the JFK Library in late September. She quickly made it clear that the film project was done for her daughter’s sake, not her own, and that she remains uncomfortable talking about herself.

“I never dreamt there would be interviews involved,” Kennedy said with a laugh. “I just thought, oh, I get to spend some time with Rory.”