For some reason — well, for an obvious reason — White House adviser Kellyanne Conway on Tuesday decided to ask a White House reporter about his ethnic background.

The reporter, Andrew Feinberg, had asked Conway to clarify what President Trump meant when he suggested that a group of Democratic women who have criticized him — all of whom are nonwhite — should “go back” to the countries from which they came. Three of the four are from the United States.

“What’s your ethnicity?” Conway responded, prompting Feinberg, clearly baffled, to ask why she wanted to know.

Because she did, Conway said, adding, “My ancestors are from Ireland and Italy.”

She later tweeted that she had asked the question of Feinberg because the majority of Americans are descended from people who immigrated from somewhere else. How that’s pertinent to Feinberg’s question — to what countries should the Democrats return? — still isn’t clear.

Unless, of course, Conway was tacitly admitting that Trump was telling, say, Rep. Rashida Tlaib (D-Mich.) to move out of Michigan and back to the West Bank, where her parents are from. Unless Conway was making clear that Trump’s description of these places of origin as “totally broken and crime infested” was a suggestion that Tlaib and Rep. Ilhan Omar (D-Minn.), a native of Somalia, have roots in places that he finds distasteful. (If he was telling Rep. Alexandria Ocasio-Cortez (D-N.Y.) to return to her mother’s birthplace, Puerto Rico, his description of the place as “broken” and “a complete and total catastrophe” takes on a new meaning.)

But as Will Wilkinson of the Niskanen Center pointed out on Twitter, Conway’s personal revelation was more revealing than she probably intended.

Conway’s mother is of Italian descent and her father, Irish. We’ve written about her mother’s grandfather before, after the White House announced plans to mandate that immigrants speak English. When Conway’s great-grandfather Pasquale Lombardo arrived in the United States in 1909, he spoke only Italian.

That year is significant: It was the peak of migration from Italy to the United States.

(Philip Bump/The Washington Post)

It is also shortly after President Trump’s own grandfather — his father’s father — returned to the United States from Germany. (He had been in the U.S. previously, but his wife got homesick. The German government thought he had been trying to dodge the draft and slated him for deportation.) By the time he returned to the United States, German migration had waned somewhat. So had migration from Ireland, which peaked in the 19th century. (It’s not clear when Conway’s Irish ancestors arrived.)

What Wilkinson pointed out was that Italian and Irish immigrants were not exactly embraced.

The spike in Irish immigrants in the 19th century spurred a broad backlash. There were worries about Irish laborers taking American jobs and concerns about the influx of Catholics. Violence broke out, and discrimination was common.

Shortly after Lombardo arrived, concern had shifted to Eastern European migrants. The plunge in immigration on the graph above in the early 20th century reflects a surge in anti-immigrant sentiment that followed World War I. But there were specific moments at which that sentiment spiked, including after a bomb exploded on Wall Street in 1920.

That incident was blamed on anarchists linked to an Italian immigrant. An editorial in The Washington Post summarized one response: The bombing “emphasizes the extent to which the alien scum from the cesspools and sewers of the Old World has polluted the clear spring of American democracy.”

Warren G. Harding, the Republican presidential candidate in 1920, warned about a deluge of immigrants with loyalties to their home country. He called such immigrants “hyphenated” — as in, “Italian-American.”

“For Americans who love America, I sound a warning,” Harding said in one speech. “It is not beyond possibility that the day might come — and may God forbid it — when an organized hyphenated vote in American politics might have the balance of voting power to elect our government.”

Harding won and quickly embraced new immigration restrictions. By 1925, the Ku Klux Klan was marching down Pennsylvania Avenue.

Italians then and the Irish before them were seen as undesirable and unwelcome. They were blamed for ruining the fabric of the United States and, often, told to go back home to the places from which they had come.

Things change. There is now an adviser to the president of the United States who is the progeny of both Italian and Irish immigrants. That, of course, is Conway — and she figured that raising her own heritage was an effective way to defend Trump’s own nativist rhetoric.

It probably wasn’t.