He admits he can have an Irish temper. If he gets heated, he may explain that his Irish is up. When he displays affection, it’s Irish warmth. A wry joke? It’s Irish humor. If he’s feeling down, it’s a “black Irish” mood.

Oh, and he’s not just Catholic. He’s Irish Catholic.

Joe Biden is many things. But there aren’t many things he is more of than Irish.

On St. Patrick’s Day at the White House, it was an Irish festival for one of the nation’s most Irish of presidents. The water in the fountain on the North Lawn turned green in the morning, and the White House was set to be lit in the same color in the evening. To start St. Patrick’s Day, Biden attended St. Patrick’s Church near his home in Wilmington, Del., before flying back to Washington for virtual meetings with Ireland’s taoiseach, or prime minister, Micheál Martin.

“Everything between Ireland and the United States runs deep,” Biden said, wearing a green tie and a fistful of shamrocks in his coat pocket. “Our joys, our sorrows, our passion, our drive, our unrelenting optimism and hope.”

President Biden spoke about U.S. ties and his own personal connections to Ireland ahead of a virtual March 17 meeting with Ireland’s taoiseach, Micheál Martin. (The Washington Post)

Biden took the taoiseach on a journey through his family genealogy, with quotes from his grandfather (“The best drop of blood in you is Irish”) and a saying that Biden claimed as his own: “We Irish are the only people who are nostalgic for the future.”

The taoiseach, who normally comes to Washington for a festive day filled with pageantry, said Biden’s election filled Ireland with pride. “Beannachtaí na Féile Pádraig!” he said in Gaelic, which means “Happy St. Patrick’s Day!”

Biden’s Irishness is more than a punchline; he uses it to frame his personal story and political identity, projecting himself as an emotional figure who knows tragedy. He uses it to explain his bursts of emotion, whether it’s a “C’mon man!” accompanied by an angry bang on the lectern, or a willingness to weep in public, or a jab followed by a wink.

And he’s not above taking a shot at the British. “The BBC?” Biden said a few months ago when a reporter tried, unsuccessfully, to stop him for a question. “I’m Irish.”

This identification with a long-oppressed minority enables him, even as a sitting president, to claim common ground with those who feel dismissed for not graduating from an Ivy League school. It lets a man who’s made millions pitch himself as “Middle-Class Joe.”

“Guys who think because they have a lot more money that they’re better than you, look down on you,” Biden said in the days before the election. “I acknowledge I got a — I have a chip on my shoulder, coming from an Irish Catholic neighborhood where it wasn’t viewed as being such a great thing.”

He connects his Irishness to his outlook on immigration, as he talks about his ancestors boarding coffin ships in the Irish Sea to escape a famine in the 1840s.

“All of our ancestors, yours and mine, they came equipped with only one thing — the only thing they had in their pocket was hope,” he said in September.

Biden also reflects on his Irish heritage in his approach to policies he views as discriminatory.

“America has come a long way in addressing discrimination in the workplace since the days my ancestors faced ‘No Irish Need Apply’ signs,” he said in a 2008 speech calling for gender equity. “Yet discrimination today still exists.”

It became a running joke among Biden’s speechwriters that most of his addresses needed to include a quote from an Irish poet — or, more often, his Irish mother (“My mother is an Irish Catholic woman with 6,000 expressions,” he has said, with perhaps a hint of hyperbole). It was through repeating phrases of Irish poetry that Biden says he overcame a stutter as a boy, and most of his major speeches have a reference to Seamus Heaney, William Butler Yeats or James Joyce.

When Biden won the presidential election, Ireland’s RTE network closed its nightly broadcast with a clip of Biden reading from Heaney’s “The Cure at Troy.”

“My colleagues always kid me about quoting Irish poets all the time,” Biden once said. “They think I do it because I’m Irish. I do it because they’re the best poets.”

During an address Wednesday afternoon to Irish Americans, Biden mixed in Irish blessings and old family yarns, meandering into a tale about his Aunt Gertie. “She did two things better than anybody else,” he said. “One is she was the best back-scratcher in the world. And two, no offense to the Greeks, but she made the best rice pudding in the world.”

Biden’s remarks were mixed with pride — noting that the White House was designed by an Irishman, architect James Hoban — and suggesting that the Irish know struggles that the world is currently undergoing.

“We have a chance to reach out, kind of like our ancestors did, to reach out and help each other,” he said. “To reach out and help people who are in trouble.”

Throughout his career, Biden has noted his Irishness in confirmation hearings and budget discussions. He has injected it into Senate floor debates and hearings on Afghanistan. He managed to quote Yeats during a hearing on U.S.-China relations.

His point isn’t always obvious. “My grandfather Ambrose’s name was Ambrose Finnegan,” Biden said during one Senate floor speech in 2001. “He used to say, ‘Remember, God protects two groups of people: well-intended Irishmen who are drunk, and the United States of America.’ ”

In 1988, while Biden was recovering from an aneurysm, Sen. Edward Kennedy — son of another famous Irish American family — took the train to Wilmington and went to Biden’s house. “He brought an etching of a big Irish stag he’d had framed. ‘To my Irish chairman,’ he’d written on it,” Biden later wrote.

On his father’s side, Biden’s family is English and French (His mother’s sister used to tell him, “Your father is not a bad man. He’s just English”). But his mother’s side has strong Irish roots.

Irish media have highlighted that 10 of Biden’s 16 great-great-grandparents were born in Ireland. The Irish Family History Center has documented Biden’s family tree, tracing it back to the Blewitts from County Mayo and the Finnegans from County Louth.

“I grew up in Scranton, in a predominantly Irish neighborhood and an overwhelmingly Irish parish,” Biden told Irish America magazine in 1987. “It was a city that had some typically eastern ethnic divisions. There was a clear identification with people being Irish; 90 percent of my class­mates identified themselves as such.”

Biden, who for decades has given eulogies for colleagues ranging from Strom Thurmond to John McCain, also attributes some of his feelings about death to the Irish wakes he witnessed in his youth.

“When I look back, I see it gave me sustenance, but I hated it,” he said in the Irish America interview. “You know, everybody sitting there drinking and the corpse in the next room. It’s brutal, when you think about it. That’s the other side, the Irishness of it, such a direct juxtaposition of life and death. There is something about the Irish that knows that to live is to be hurt, but we’re still not afraid to live.”

Ironically, most of Biden’s relatives have never been to Ireland, he once said, but in 2016, when he was vice president, Biden took his family to visit the country.

“James Joyce wrote, ‘When I die, Dublin will be written on my heart,’ ” Biden wrote in a letter before the trip. “Well, Northeast Pennsylvania will be written on my heart. But Ireland will be written on my soul.”