New York Giants linebacker Mark Herzlich grew up in locker rooms, from peewee football to the NFL.

“It’s a very unusual work environment — a small space and 100 percent male,” Herzlich said.

Locker to locker, the setting is marinated in machismo, with a lineup of employees celebrated for their toughness.

“We play a rough game on TV,” Herzlich said. “People see us and say: ‘Man, look at that dude. That’s a guy right there.’”

In recent seasons, as the NFL was shamed by multiple domestic violence arrests and the incendiary video of running back Ray Rice punching his then-fiancée in an elevator, Herzlich knew it was crucial that he work to change the culture of the locker room.

“In the beginning, you’d call people out and tell them that something they said — locker room talk — wasn’t really funny,” Herzlich said last week, sitting on the living room couch of his New Jersey home. “There would be jokes or something denigrating to women. It would be the kind of thing they would never say in front of a woman, but since it’s all men, they thought it was OK.”

It was not OK with Herzlich, and he had a specific reason.

Five years ago, his then-girlfriend and future wife, Danielle, sat him down and revealed something she had kept hidden. Danielle explained that she had been physically and emotionally abused by her father from age 9 until she was 15.

“It was very serious physical abuse — punched in the face and beaten up,” Danielle said as she sat at home next to Mark and spoke publicly about the abuse for the first time. “It did not stop until my father was arrested and jailed, which was the last time I saw him.”

Efforts to contact Danielle’s father were unsuccessful.

Danielle’s revelation was a thunderbolt to Mark, who in the years since has emerged as one of the NFL’s more forceful advocates of raising players’ awareness of domestic abuse.

“I thought domestic violence was something rare that happened to other people,” he said. “Danielle’s story changed my entire outlook. Yes, the majority of men don’t commit violence against women, but men overall need to stand up to other men. Don’t just hold yourself accountable. Hold others accountable to treat women how they deserve to be treated.”

Mark and Danielle Herzlich have become volunteers for a variety of domestic violence awareness groups, with Mark starring in public service announcements for the domestic abuse awareness campaign No More. The PSAs were directed by the “Law and Order: Special Victims Unit” television actress Mariska Hargitay, who 11 years ago established the Joyful Heart Foundation to aid survivors of sexual assault, domestic violence and child abuse.

Hargitay and the Herzlichs have since worked together on other projects. One idea was to stage a domestic violence awareness event at a Giants home game.

“It’s imperative that the issue is out in plain sight instead of keeping it behind closed doors,” Danielle said. “We have to change the culture. I know I did not want to talk about it for so long. I did not want people to feel sorry for me.”

Pity is what Danielle and Mark were both trying to avoid when they met as Boston College students in 2009.

Danielle was protecting a family secret, fearful of being seen as a victim. Mark had recently learned he had a rare and life-threatening bone cancer, Ewing’s sarcoma. Mark, an all-American football star, was told by his doctors that his football career was very likely over. He might never run again. Chemotherapy soon robbed him of his hair and weakened his muscular, athletic frame.

“I lost my identity,” Mark said. “But the worst was people looking at you and seeing only someone with cancer.”

Since he was already bald, Mark decided to dress up for a Halloween party as Mr. Clean, a costume he made complete with a white shirt and white pants. At the party, he met Danielle, who had heard of the football star Mark Herzlich but did not know she was talking to that Mark Herzlich.

“Football never came up; I got to know this person named Mark,” she said. “He was going through so much with his illness, and there was a connection because he talked about not wanting to be viewed as a cancer victim. I could relate to that.”

Over time, as a relationship bloomed, Danielle decided to tell Mark about her childhood.

“I felt safe with him — that’s why he was the first guy I ever met that I told my story to,” Danielle said.

The couple married during this past offseason.

Mark made a remarkable recovery and played one last season at Boston College in 2010. Although he was free of cancer — and has remained so — his stock with NFL teams dropped precipitously. Once considered a potential first-round draft pick, he was not selected by any NFL team and signed with the Giants as a free agent, making him a long shot to make the roster.

But Herzlich played in 11 games as a rookie in 2011, a Super Bowl-winning season. His story was chronicled by “60 Minutes” and other media outlets. Now a valued veteran presence on the field, he has played in 53 games.

“Mark taught me that it’s OK to be proud of being a survivor,” Danielle said.

In 2012, the couple attended a My Sisters’ Place charity dinner at which a speaker told the audience about the domestic violence she had endured.

“I heard someone describe exactly what I went through, which was an overwhelming experience, because you often feel like you’re alone,” Danielle said.

On the car ride home, Danielle told Mark she wanted to use her story to help other domestic abuse survivors.

“Something so horrific, as hard as it might be to tell and live again, can have a positive impact on others,” said Danielle, who began making herself available to speak to small groups of women brought together by domestic violence support groups.

At a My Sisters’ Place dinner in 2013, before a gathering that included Giants coaches, executives and many of the team’s players, Mark delivered a speech that explained what Danielle had gone through.

“There must have been 50 people who came up to me afterward and told me they were abused,” Danielle said. “It was heartbreaking, but at the same time, you could feel the power of having made that connection.”

Mark said scores of teammates have since talked to him about the meaning and impact of his speech. It seemed all the more relevant last season when the NFL faced bitter criticism for the transgressions of multiple players.

“Last year, it was a tragedy that was happening in our league,” Herzlich said. “And sometimes tragedies open a gate to call attention to a problem. It is important that a football player stands up and says we have to do more to protect women.

“Whether the guys realize it or not, we have an opportunity. We can show people that we have a tough job but that isn’t what shapes you inside.”