Fifteen students gathered inside a basement classroom at Catholic University on a recent evening to ponder a laminated vocabulary list that looked like some language instructor’s cruel joke.

The words were jumbles of seemingly random letters, strings of unpronounceable consonants, like the work of a touch typist who inadvertently plants his fingers on the wrong keys.

But for these students, and for kindred spirits in America and Ireland, the Irish language has emerged as an improbable passion.

As the Irish diaspora prepares for St. Patrick’s Day, the Hibernian tongue, once at the brink of extinction, is enjoying a modest revival. A 2009 survey by the Modern Language Association found enrollment in Irish-language classes in the United States numbered 409 students, compared with 278 in 1998, 58 in 1990 and 28 in 1980. Classes at Catholic University drew 18 students this year and 20 last year, the largest enrollments in recent memory.

Catholic may be the only college in the Washington region that has ever mounted a significant Irish language program. The effort is one of the oldest in the nation, funded through an 1896 gift of $50,000 from the Ancient Order of Hibernians.

“I actually put my Facebook page into Irish,” said Bridget McCarthy, 19, a sophomore from Howard County who plans to major in archaeology — Irish archaeology. “It will probably be easier to learn the ancient language if I learn the modern one,” she said.

Irish, or Irish Gaelic, has resurfaced as a subject of scholarship in classrooms and social conversation groups after gradually disappearing from everyday vernacular in pubs and homes.

Waves of immigration planted hundreds of thousands of Irish speakers in American cities in the 19th century. They died off, and their descendants fled to the suburbs, seeding the collapse of traditional Irish American culture.

Irish declined in Ireland, as well; generations of British rule drove the number of native speakers below 100,000. But now the language is enjoying a renaissance. Irish-language immersion schools have sprung up across Ireland in recent years, spawning a new generation of young, bilingual Irish adults.

The gaelscoil, or Irish-language school, has proven inordinately popular among Ireland’s elite, and many schools keep waiting lists. A report in the Irish Times newspaper said the movement had taken hold there not only in remote hamlets but also with affluent helicopter parents swept up in a “post-Riverdance cultural zeitgeist.”

“There’s kind of a seismic change taking place in Irish identity,” said Traolach O’Riordain, director of Irish studies at the University of Montana. “It’s more common to hear the language spoken in cities now, compared with 30 or 40 years ago . . . These kids are coming out and they’re forming Irish-speaking clubs and associations.”

Ronan Connolly, 31, taught at a gaelscoil in his native Monaghan, Ireland, before coming to the United States four years ago. Now he functions as a sort of one-man Irish heritage society. Connolly took over the Irish course at Catholic in the fall. He also teaches Irish classes out of an office in Friendship Heights. In his short time in Washington, Connolly has coordinated an annual Irish film festival, produced an Irish music podcast series and played Gaelic football with the D.C. Gaels.

No one was more surprised than he at the success of the Irish classes. “I had come across this notion that Americans aren’t interested in learning other languages,” he said.

Yet, Connolly’s students at Catholic are learning this most difficult tongue chiefly for their own enjoyment. There are few places, even in Ireland, where they will have much hope of speaking the language once they have learned it. Ireland’s Gaeltacht, or Irish-speaking district, is concentrated in the counties of Donegal, Galway and Kerry, although most Irish schoolchildren learn some Irish.

Irish survives in American classrooms as a “heritage language,” embraced by fourth- and fifth-generation immigrants to counter decades of assimilation. The same impulse has buoyed Italian and Polish, said Rosemary Feal, executive director of the Modern Language Association.

“Do you think you want to introduce yourself to class today?” Connolly asked, addressing a cluster of students in his classroom at Catholic on a recent evening. His query was met with a polite shaking of heads; it was the third class, and it would be the group’s first time speaking Irish in public.

“This is a language I’m sure you’ve never heard before,” he told the class. “And it doesn’t sound the way it looks, and it doesn’t look the way it sounds.”

Irish resembles other Celtic languages. But to native speakers of English, it is about as familiar as Klingon. Consonants tend to come in pairs, with the tongue pulled back to pronounce the first letter and pushed up to form the second, producing a sort of gutteral texture not unlike the cadence of Russian. Sentences are formed with verb, subject and object in sequence, more akin to Spanish than English. “I see you” becomes “See I you.”

The language is a landmine of silent letters: a silent “f” in glanfaidh, and a silent “d” in beidh. (“It’s just like bay, like ‘Baywatch,’ ” Connolly told his students.)

One student paused on the vocabulary term scriobhfaidh for a long moment and then shrugged, “I have no idea how to say that.”

Daniel White, a 21-year-old senior from Long Island, thought Spanish was difficult until he took up Irish.

“The pronunciation doesn’t match up with how the words look even a little bit,” White said.

White is Irish American, and one of a few in his clan who have not been back to Ireland. He enrolled in the course, he said, out of a “renewed sense in discovering one’s own heritage. A lot of my older relatives are very excited about it.”

An informal survey of several dozen colleges in the District, Virginia and Maryland found no other campus with an Irish language course. Substantial Irish programs exist at New York University, Notre Dame, the University of California at Berkeley, the University of Pittsburgh and the University of Montana, whose five-year-old program now serves 187 students.

Irish is rare, but most world languages are rarer still. Modern Greek language enrollment, for example, totals 152 students, according to the national survey; Danish, Finnish and Hungarian are even less common.

Irish is not even the most esoteric language studied at Catholic. Aspirant scholars of early Christianity at the Northeast Washington campus study Aramaic, Coptic, Syriac and Akkadian, because “those are the languages that the texts are in,” said Lawrence Poos, dean of the school of arts and sciences. “I’m pretty sure we still do Ugaritic.”